FOUND IN THE GAULT OF THE EASTERN
Mr. H. E. SAUVAGE*
ON THE REPTILE LOCALITY IN THE GAULT OF THE EASTERN PARIS BASIN
In the Paris Basin, east and south of this basin, the Albian terrain forms a continuous band “from the banks of the Oise to the environs of Hirson (Aisne), along the Ardennes, Meuse, Marne, Haute-Marne, Aube, Yonne and up to the Nièvre. North of this basin it was encountered in a sufficient number of surveys so that one could admit that it is represented on this side near Valenciennes and Douai by a continuous series of isolated outcrops; subsequently its presence is noted on the bank of the Wissant and on the interior circumference of the Bas-Boulonnais and the Bray country, in the wells of Meulers at Rouen, and in all the drillings of the center of the basin that the Cretaceous traverses1.”
In the first studies on the Cretaceous terrain, Mr. Charles Barrois reunited the Aptian and Albian in the same stage under the name Gault1 after the examples of Ewald, von Strombeck, Credner, and Schlüter. Mr. Barrois has since maintained the separation between the two stages; for him, the Aptian as Orbigny extended it corresponds to the Pebble Beds of Godalming, Upware, Farringdon and Potton in England and to the Lower Greensand above the Pebble Beds. The Albian can be separated into three zones from bottom to top: the Ammonites mammillaris zone, corresponding to the Folkestone Beds and the upper part of the Lower Greensand; the Ammonites interruptus zone, corresponding exactly to the Gault of Cambridgeshire and the lower Gault of Folkestone; the Epiaster ricordeanus and Ammonites splendens zone, which is gullied by the Ammonites inflatus beds passing between the Albian and Cenomanian.
The Gault is well known in the eastern part of the Paris Basin due to the works of Messrs. d’Archiac, Hébert, Buvignier, Nivoit, and Ch. Barrois; its very rich fauna has often been studied by d’Orbigny; indeed, Mr. Charles Barrois, without accounting for echinoderms, bryozoans, and sponges, enumerated more than 320 species; of this number only 1/15 were common to the three divisions of the Aptian, such that it must be concluded that these divisions are real and very distinct from one another. Some vertebrates were also recovered in the Gault; Mr. Barrois noted 18 species of fishes (5 Pycnodus; 3 Chimaera; 4 Otodus; 1 Lamna; 4 Odontaspis; 2 Sphenodus; 1 Myliobates) in the Albian stage; 3 species of reptiles are indicated in the Aptian, 9 in the Albian, and 1 in the Ammonites inflatus zone at the base of the Cenomanian.
To my knowledge, Mr. Charles Barrois is the first to gave a reasoned list of reptiles found in the Gault of the Paris Basin2.
These reptiles, numbering 10 species, are:
APTIAN: Megalosaurus sp.; Plesiosaurus latispinus Ow.; Polycotylus sp.
ALBIAN. Greensands with Ammonites mammillaris: Megalosaurus sp. (Louppy in the Meuse, Grandpré in the Ardennes); Hylaeosaurus armatus Mant. (Grandpré); Pterodactylus segdwicki Ow.? (Louppy, Grandpré); Ichthyosaurus campylodon Cart. (Louppy, Grandpré); Plesiosaurus latispinus Ow. (Louppy); Plesiosaurus pachyomus Ow. (Grandpré); Pliosaurus sp. (Grandpré); Polyptychodon interruptus, Ow. (Louppy, Grandpré).
NODULES with Epiaster ricordeanus: Polyptychodon interruptus Ow. (Ardennes and Meuse); Pterodactylus compressirostris Ow.
CENOMANIAN. Ammonites inflatus zone: Polyptychodon interruptus Ow. (Ardennes and Meuse).
Mr. Barrois remarked that some of the reptile bones found in the Ammonites mammillaris zone are impregnated with limonite and probably come from the Aptian mineral; they were altered; in particular, such are the remains that must be referred to Polycotylus.
Thanks to the kindness of Mr. Barrois, in 1876 I described several of the species found in the Ardennes and the Meuse, and figured what was known then of the megalosaur and Polycotylus1.
Such was the state of the question of the reptiles of the Gault of the eastern Paris Basin, reptiles that were hardly known except by some fragmentary debris, when, by the benevolent intervention of Mr. Albert Gaudry, Mr. Louis Pierson wanted to subject to my examination a very remarkable collection of reptile bones recovered by him in the Gault of Louppy, in the Meuse; this collection included indeterminate plesiosaur, ichythosaur and crocodilian bones and a large part of the skeleton of a megalosaur clearly distinct from the Great Oolite species. Mr. Péron also gave me the friendship to entrust me with the study of the reptiles found in the Ammonites mammillaris zone of Grandpré (Ardennes) and Villotte (Meuse). Mr. Charles Barrois communicated to me the reptiles catalogued in his different publications on the Cretaceous of the northeast part of the Paris Basin.
I have just said that the reptile bones recovered by Mr. Pierson were found in the Pentiève phosphate locality, commune of Louppy-le-Château (Meuse). It results from the information communicated by Mr. Pierson that, “the megalosaur bones were found in a well dug 10 meters deep in a sandstone that was found mixed with the phosphate beds; the animal was complete, because still other bones were seen that were impossible to reach because of the crumbling of a part of the galleries where the air pockets were produced. All the bones followed one on the other, but were broken by the load that weighed on them. Regarding the other bones, they were recovered in different wells of the same locality, but always at the same depth, rather more than less, because I remarked that the bones were almost never found in the open ones, nor in the wells approaching the beginning of the phosphate banks.”
Regarding the locality, Armand Buvignier2 notes that, “the greensands and clays of the Gault deposited above the Portlandian limestones in the cantons of Varennes, Clermont, Triaucourt, and Vaubecourt, and on the Neocomian terrains in the cantons of Bar and Tevigny (Louppy-le-Château is in this canton), are extended in isolated outcrops at the surface of the Portlandian plateau, east of Vaubecourt and on the right bank of the Aire. This terrain, which occupies a surface of 413 square kilometers, is composed of clay bases resting on the Neocomian stage and covered by greensands and gray or blue clays. The fossils that are found belong to nearly all diverse orders of acephalic molluscs; some serpulids, belemnites and debris of fishes and saurians have been recovered; numerous fucoids have also been recovered. The fossils found up to the present in the greensands of the Meuse department belong to the following species:
“Fucoids. Diastopora. Alecto granulata. Crustaceans. Serpula filiformis. Serpula indet. Pholadomia moraeana. Panopaea prevosti. Lucina. Astarte. Corbis cardiformis. Cardium. Pinna. Ostrea leymerei. Gryphaea. Exogyra harpa. Anomia. Terebratula moraeana, praelonga, depressa. belemnites.”
In the same beds as the reptiles that I will describe below, Mr. L. Pierson recovered numerous fossils that, according to Mr. Dr. Trémaux de Rochebrune, belong to the following species:
Ammonites lautus Park.
“ tardefurcatus Leym.
“ serratus Park.
“ mammillaris Schl.
“ auritus Sow.
“ beudanti Brong.
Hamites attenuatus Sow.
Scalaria clementina d’Orb.
Natica laevigata d’Orb.
“ gaultina d’Orb.
“ rauliniana d’Orb.
“ lamellifera Rochbr.1
Pleurotomaria neocomiensis d’Orb.
Phasianella gaultina d’Orb.
Rostellaria parkinsoni Mant.
“ carinella d’Orb.
Teredo serpuloïdes Rochbr.2
Panopaea plicata d’Orb.
Venus vibryeana, d’Orb.
“ rotomagensis d’Orb.
Opis hugardiana d’Orb.
Trigonia fittoni Desh.
“ aliformis Park.
Nucula ovata Mant.
“ pectinata Sow.
Arca carinata Sow.
“ hugardiana d’Orb.
Mytilus cuvieri Math.
Lima rauliniana d’Orb.
Inoceramus concentricus Park.
Pecten dutemplei d’Orb.
“ raulinianus d’Orb.
Plicatula radiata Lamk.
Ostrea aquila d’Orb.
“ milletiana d’Orb.
“ rauliniana d’Orb.
Rhynconella sulcata Park.
Heteropora digitata Mich.
Ostrea aff. ramosa Sow.
This clearly Albian fauna is entirely from the lower, or Ammonites mammillaris, zone. Of the 50 species that I can compare with the list given by Mr. Barrois1 I find 23, or 76.6%, in this zone; 22 species, or 73.3%, are found in the Ammonites interruptus zone, 12, or 40.0%, in the Epiaster ricordeanus zone. There are 10 (33.3%) species in common between zones 1, 2, and 3, 9 (30.0%) between zones 1 and 2, no species in common between zones 1 and 2, and a single species in common between zones 2 and 3; there are 5 species from the list given above that are unique to zone 1, 4 unique to zone 2, and none are unique to zone 3.
STUDY OF THE REPTILES FROM THE GAULT OF THE EASTERN PARIS BASIN1.
PTERODACTYLUS SEDGWICKI, Owen2.
(Pl. II, FIG. 7, 8.)
The presence of the genus Pterodactylus in the Ammonites mammillaris greensands of the Gault from northeast France is indicated in a certain manner by the discovery of a cervical vertebra made at Louppy (Meuse).
This nearly intact vertebra entirely resembles the element figured by Owen as Pterodactylus fittoni or sedgwicki (Loc. cit., Pl. II, fig. 18). It is known that these two species, whose remains are mixed at Cambridge, are very close and that their size is the same; they can only be distinguished from one another in that the alveoli are closer together in P. sedgwicki than in P. fittoni; because of the resemblance to the teeth that I describe below with those of P. sedgwicki, I am entirely disposed to refer to this latter species the vertebra that I describe (fig. 8).
This vertebra is exactly the same size as the element figured by Owen, 0.043 m long; the straight ventral surface, as contracted in its median part, presents a weak longitudinal projection anteriorly, the vestige of a hypapophysis; it is slightly indented posteriorly. The slightly tall lateral surfaces are excavated by a furrow between the lateral edge, which is sharp, and the transverse processes. The base of the neural arch is wide and robust; its cross-section is triangular. The neural canal is oval. The very well-preserved posterior articular part advances markedly in front of the marrow cavity, 0.011 m; at its end it presents a sort of rounded pad, under and on each side of which are seen the postzygapophyses. The prezygapophyses are extended anteriorly (fig. 8, 8 a, 8 b).
Mr. Ch. Barrois also recovered some teeth coming from a pterodactyl the size of P. sedgwicki in the Ammonites mammillaris zone of Grandpré (Ardennes); except for several slight differences that I will indicate, these teeth entirely resemble the element figured by Owen under no. 11 of plate I of the cited monograph.
These teeth, which unfortunately are incomplete, not one having preserved either the root or the point, are very slightly recurved anteroposteriorly, flattened mediolaterally, and gradually thin toward the apex; one of them is 0.011 m in anteroposterior diameter and 0.007 m in mediolateral diameter. The enamel covering them presents a sort of irregular folding due to the presence of small, very irregular longitudinal folds that are fused and divided without order, thus forming an irregular a network with long and very straight meshes on both sides of the tooth. The width of the folds is the same as that of the depressions between them. The transverse cross-section of the teeth is elliptical, but there is a sharp carina that separates the two surfaces (fig. 7).
“These teeth are very similar to those of Pterodactylus sedgwicki described by Owen; the only difference is the carina that separates the two surfaces of our teeth, and whose existence Owen did not note in the teeth he described. These teeth thus belong perhaps to a new species, but it should be remarked that the fossils from the Gault and Cambridge are often rather poorly preserved, according to Owen; this carina could therefore have been worn on his samples. A tooth of Pterodactylus compressirostris that I discovered in the glauconitic chalk with Am. inflatus at Folkestone, and which is in a good state of preservation, presents at its base all the characters assigned by Owen to this species, a regular ellipse with rounded surfaces on both sizes and without carina; but in advancing toward the apex, the tooth gradually presents the characters that distinguish the Grandpré teeth, that is the double carinae. I think therefore that the Grandpré pterodactyl should be considered the same as that from Cambridge1.”
Preceded in the Triassic by the genus Teratosaurus2, megalosaurs appear to originate via a small-sized species in the time during which the infra-Liassic sandstones of La Moselle were deposited3; more abundant in the Inferior Oolite system and in the Great Oolite, they are represented during the Upper Jurassic period, Kimmeridgian and Portlandian, by Megalosaurus insignis1 and meriani2, to be continued in the Wealden, that is the base of the Cretaceous, by a species of great size; this last species, for which the English paleontologists, Mr. Owen in particular, have preserved the name Megalosaurus bucklandi, is indeed very close to its congener from the Bathonian system. Phillips also only admitted one species, “The Megalosaurus bucklandi,” he wrote, “is a great predatory Lacertilian whose remains were found, in England, at Lyme Regis and Wachet (Lias); near Bridport (Inferior Oolite); at Stonesfield (lower part of the Great Oolite); at Enslow Bridge (upper part of the Great Oolite and Forest Marble); at Weymouth (in the Oxford Clay); at Cowley and Dry Sandford (Coral Rag); at Malton in Yorkshire (coralline Oolite); and in Sussex (Wealden). The species was recovered in the Kimmeridge Clay of Honfleur in Normandy, and in the Oolite of Besançon3.”
As I have shown, with Messrs. E. E. Deslongchamps and Lennier, the Kimmeridgian megalosaur is clearly distinct from Buckland’s megalosaur, although it is still only very imperfectly known; it is the same as the Gault megalosaur.
The first mention that I know of a megalosaur at this latter level is due to Mr. Boyd Dawkins, who noted the presence of the genus in the Liassic of Lyme Regis, the Oolite of Dorset, the Kimmeridge Clay, the Wealden terrain and the Lower Greensand of Potton; also Mr. Seeley indicated the discovery made in this latter locality of a skull of a great reptile, probably a dinosaur, but could not make a generic determination of this skull fragment, also it was Mr. Charles Barrois who first noted in an unquestionable manner the presence of the megalosaur genus in the Gault (Ammonites milletianus zone, Ammonites mammillaris zone) of the Ardennes and Meuse. Indeed, three teeth have been recovered at Grandpré and Louppy with Am. Mammillaris. “These teeth,” wrote Mr. Barrois, “are strong, laterally compressed and in the form of a saber point; they are recurved and saw-toothed on their edges. The teeth of Megalosaurus bucklandi, the only species known by the English naturalists, is very close to those that we possess; we believe them to be different, however; the Gault megalosaur belongs, according to us, to a new species4.” I was able to study these teeth and note that they indicate a species that, although very distinct from Megalosaurus bucklandi from the Great Oolite and Wealden, is similar to Megalosaurus insignis from the upper part of the Jurassic terrains1.
The teeth from the anterior part of the jaw of Megalosaurus insignis that resemble the tooth coming from the Cretaceous of Gosau and figured by Mr. Seeley under the name Megalosaurus pannoniensis, n. sp2. This small tooth, 0.021 m, is recurved like the tooth of Megalosaurus insignis to which I compared it. On the anterior edge exist fine, equal serrations that extend only along half the length of this rounded edge, just as the cross-section of the tooth is exactly the same as in typical megalosaurs; the serrations extend along the entire length of the posterior edge.
MEGALOSAURUS SUPERBUS Sauvage.
Only the anterior part of the megalosaur skull being known up to now, I describe the articular part of the mandible, based on an element in the Pierson collection. This piece shows us that in the megalosaur, just as in all saurians and the inverse of what is seen in crocodilians, the complementary* forms only a coronoid process far from the condyle; as exists in saurians, this process must have appressed against the salient process that provides the jugal. The coronoid process is little elevated above the edge that forms the anterior part of the complementary, which is extended rather far anteriorly, its upper edge being on the same level as the medial edge of the dentary.
The articular part of the complementary forms a depressed surface directed posteriorly, partly ventrally and a little medially. Below this depressed surface, the lateral face of the bone is excavated, as is seen in saurians, this excavation is extended onto the surangular. Just as in saurians, a crest borders the complementary posteriorly, however less strong than it is in these latter. On the lateral face, the surangular appears to be extended to the end of the complementary, as exists in saurians,.
The restoration of the megalosaur skull given by Phillips3 shows the process formed by the complementary, the jaw being restored according to the varanid type; if the mandible of Buckland’s megalosaur was similar to that of the species found in the Meuse, the process is too elevated and too vertically directed on this restoration.
In the megalosaur from the phosphates, the mandible is hardly thick, only 0.028 m at 0.160 m from the coronoid process, and does not attain more than 0.070 m in height at this point.
(Pl. II, fig. 3, 4, 5.)
As I said previously, in 1875 Mr. Barrois established the presence of the genus Megalosaurus in the Ammonites milletianus and mammillaris zones of the Ardennes and Meuse by the discovery of entirely typical teeth found at Grandpré and Louppy.
The tooth recovered in this last locality is laterally compressed in the form of a saber point. The anterior edge is sharp along its entire length, garnished with fine, serrated denticles; the nearly straight posterior edge is equally sharp and provided along its entire length with serrations of the same size as those of the anterior edge. The cross-section of the tooth is regularly oval; however, the lateral faces are little more compressed near the posterior edge than toward the anterior edge. The surface of the tooth is traversed by fine striations directed apically. The peak is trenchant and acute. This tooth is 0.070 m tall and 0.023 m wide at the base (fig. 3).
Two teeth still in place in the jaw, and forming part of the Pierson collection, show clearly that the enamel serrations are continued down to the base of the tooth, as much on the anterior carina as on the posterior. These teeth, more curved than those just described, have lengths of 0.055 m for one and 0.050 m for the other (fig. 4).
According to Pictet, “in megalosaurs the dental enamel only descends a short distance from the apex1.” In writing these lines, Pictet evidently had Buckland’s megalosaur in view. Indeed, in this megalosaur the serrations of the posterior edge stop well above the base, the tooth being entirely intact besides and still enclosed in its replacement alveolus2. Pictet further indicated that in megalosaurs, “the teeth, at their birth, are straight and compressed into a saw-blade on their edges.”
I made known, after Messrs. Deslongchamps and Lennier, under the name Megalosaurus insignis a species from the Kimmeridgian terrain of Havre and Boulogne whose teeth offer this characteristic that the serrations of the posterior edge descend to near the base; moreover, the adult teeth present all the characters assigned by Pictet to teeth having newly left their alveoli, that is, they are straight. The same characteristic is noted on a tooth from Louppy, so that it is interesting to note the type of alternation of megalosaurs from diverse geological levels, the Wealden species recalling Megalosaurus bucklandi from the Great Oolite, and the Gault megalosaur having some affinities in the teeth with Megalosaurus insignis from the Kimmeridgian and Portlandian.
In the Upper Jurassic megalosaur, the teeth from the anterior part of the jaws are only serrated along a small part of the anterior edge; however, I have noted some teeth coming from the same portion of the jaws on which the serrations are continued very low. For the Gault megalosaur, the serrations are extended to the base in the anterior teeth, both on the anterior and posterior edges (fig. 5).
The characters that I have just indicated are found in the teeth recovered at Grandpré by Mr. Péron.
I only know of a few vertebrae belonging to Megalosaurus superbus; they come from a young individual and are similar to those of Megalosaurus bucklandi.
The dorsal vertebrae, of which only the centra remain, entirely resemble those figured by Phillips1. The centrum is strongly excavated longitudinally, as well as on the lateral surfaces. The articular surfaces, markedly rounded (bi-transverse diameter 0.065 m; height 0.068 m) are directed obliquely from top to bottom and slightly excavated; the edge is thin. The ventral surface continues in a regular curve with the lateral surfaces.
A vertebra, perhaps the first caudal, has one of its articular surfaces flat, whereas the other is strongly concave; this vertebra is 0.058 m long; the surfaces are obliquely directed.
The lengths of the vertebrae that I have been able to study are 0.053 m; 0.056 m; 0.058 m; 0.062 m; 0.065 m; and 0.065 m.
Judging by several fragments, the spinous process appears to have been relatively thin; the end of this process is slightly dilated.
I possess only a 0.060 m long vertebral fragment from the sacrum; the cross-section of this vertebra is triangular, the ventral angle being rounded; the lateral surfaces are slightly excavated; this vertebra entirely resembles the element figured by Phillips2.
One caudal vertebra is 0.075 m long, narrowed in its medial part. The ventral surface is excavated as a whole, as are the lateral surfaces. The oval articular surfaces are slightly excavated, above all in their dorsal part; they are all of both the same form and the same dimensions. The base of the neurapophysis is wide and extended along most of the centrum length, however less than in Eucercosaurus tanyspondylus figured by Seeley3, by forming a crest accentuated above all in the median part. The facets for the chevron bones are rather large and oval; these facets are separated from one another by a narrow space.
This vertebra much resembles that of Eucercosaurus from the same level, but differs in the elongated oval and not circular form of the articular surface.
By comparison with the vertebra of Eucercosaurus, the vertebra that I describe must come from the posterior part of the tail.
The ribs, of which I have only some debris, are similar to those of Megalosaurus bucklandi. The anterior dorsal ribs are long; the head presents two extensions for articulation with the centrum and the vertebral lamina; these two rami diverge from one another at a very open angle; the shaft of the rib itself is slightly arched; this rib is 0.027 m thick and presents a salient crest in its median part, so that its cross-section is markedly prismatic.
(Pl. IV, fig. 2.)
The clavicle greatly resembles that of Buckland’s megalosaur; it must be of great size, based on the fragment that I have; indeed, the width of the bone is 0.060 m in its middle part. The pectoral edge is more curved than in Megalosaurus bucklandi; the ventral edge is less indented than in this last species; this edge, trenchant in its more medial part, is rounded little by little.
(Pl. IV, fig. 1.)
We have the inferior end of this bone, for a length of 0.160 m. The cross-section of the bone is transversely oval, the two diameters being 0.060 m and 0.043 m. The posterior or inferior surface is flat, and the other surface is rounded; however, toward the distal end the lateral part of this anterior surface flattens, whereas the medial portion is rounded. The distal articular surface is 0.110 m wide and curved into a slightly open S-shape, the medial part being much thicker than the lateral; on the posterior surface, near the articulation, a rather wide depression is seen, like in the iguana but relatively shallower (fig. 1, a).
(Pl. I, fig. 4, 5,; Pl. II, fig. 1.)
The metacarpals are known only from two 0.120 m long fragments, showing the proximal articular surface. This surface has the form of a triangle whose peak is directed medially; it is slightly bent as a whole. The dorsal face of the bone, which is slender and elongate as in crocodilians, is convex, flat near the proximal end, above all toward the lateral face; the medial face is nearly flat.
Mr. Pierson found in a block with some teeth, a femur, fragments of ribs, the tibia and vertebrae, most of a manus and some detached manual bones from the opposite side of an animal that I am authorized to refer to the megalosaur.
This manus (Pl. II, fig. 1), which comes from a still-young individual like all the rest of the bones found by Mr. Pierson in his first excavations, is composed of three digits, probably 2, 3 and 4, this last very incomplete.
The second digit (2), composed of three phalanges, is 0.095 m long. The ungual phalanx un, of which only the imprint remains, is long and straight and must have ended in a sharp claw. The phalanx preceding it is rounded on its dorsal surface (pl.). The first phalanx, 0.055 m long, has an excavated proximal articular surface; the lateral surfaces are slightly indented; the dorsal surface is flat near the proximal end; the distal articular surface presents without doubt an articular pulley; near this end, and against the dorsal surface, can be seen a rather deep cavity (ph. 2).
I count four phalanges in the third digit (3). The ungual phalanx, much shorter than in the second digit, bears a straight and sharp ungual in the form of a claw (un). The third phalanx is shorter, narrower, and a little more convex in its medial part than the corresponding phalanx of the second digit pl. The second phalanx, different from the phalanx of the second digit, is 0.028 m long; it is slightly excavated longitudinally; the distal articular surface, a little excavated bilaterally, thus presents an articular trochlea; the proximal articular surface is rounded (ph. 3). The first phalanx has a concave articular surface; the proximal articular surface is slightly convex; the superior surface is excavated anteroposteriorly; the length of this phalanx is 0.028 m (p. 3).
The fourth digit, whose phalanges are not in place, shows only two phalanges and the end of the metacarpal. The articular head of this bone is widened in an irregular shape, with a salient part near the anteromedial angle (mt. 4). The subsequent phalanx, 0.025 m long, is narrowed at one of these ends, which is regularly rounded, the other end being obliquely cut (p. 4). The other phalanx, very incomplete, shows that the articular end is cut obliquely to be adapted to the articular surface of the corresponding phalanx (ph. 4).
The Pierson collection also includes several detached phalanges coming from a non-adult animal.
One of these bones (Pl. I, fig. 5) belongs without doubt to the lateralmost digit. The dorsal surface, the straightest, is flat and widened at its distal end; the ventral surface is slightly concave in its posterior part, slightly convex, in contrast, in its anterior part. The lateral surface is flat, slightly separated from the ventral surface in its posterior part, and merging with this one in its middle part. The entire ventral surface is excavated. The slightly convex proximal articular end is wider in the ventral part than in the dorsal part (fig. 5). The distal articular end is rounded transversely (fig. 5 a).
The bone figured under number 4 of plate I is the first phalanx of the third digit; it is seen in the drawing by its ventral surface. This bone is 0.045 m long; its width in the posterior part is 0.022 m, its thickness is 0.025 m; in the anterior part the width is 0.016 m, the thickness 0.014 m. The dorsal surface is flat, however slightly excavated anteroposteriorly in its whole. The flat medial surface is separated from the dorsal and ventral surfaces by a well-marked edge, above all in the posterior part. The lateral surface is rounded and merges insensibly with the dorsal and ventral surfaces. The distal articular end presents a trochlea (fig. 4 a). The wider proximal articular surface is excavated transversely so that the two articular condyles are placed directly on top of one another, continuing the dorsal and ventral surfaces, the ventral condyle being the more salient.
Along with these bones, Mr. Pierson found a bone that I can only refer to the megalosaur with doubt. This bone, figured under number 3, 3a of plate III, is 0.045 m long. The clearly quadrilateral proximal articular surface is slightly convex. The distal articular surface presents a trochlea; the lateral condyle, more salient than the other, is less extended dorsoventrally; indeed, the medial condyle is continued as a pulley to behind the lateral condyle, so that in regarding this bone by its ventral surface one sees this condyle along the lateral edge. The dorsal surface presents the two condyles at its anterior end, the condyles separated by a rather deep gorge; this surface is excavated in its posterior part. The ventral surface shows the largest part of the lateral condyle; it is deeply excavated between this condyle and the posterolateral angle.
(Pl. I, fig. 1.)
I was able to study a femur that is 0.500 m long and comes from a still-young individual. This femur greatly resembles that of Megalosaurus bucklandi figured by Mr. R. Owen; however, the articular surface for the tibia is rather different in the two species; the tibial edge is more excavated, and the two condyles are separated by a well-marked notch in the species from the phosphates; the lateral condyle is as much extended as the medial, which is more rounded than in the megalosaur from the Great Oolite of England.
The neck supports the trochanter and head of the bone. Semi-spherical in form, turned a little backward, this is the termination of a portion of the end of the bone that is anteroposteriorly, mediolaterally, and dorsoventrally flat; the posterior surface, at the same time a little lateral to this part, is continued with the posterior surface of the shaft of the bone; the anterior surface, at the same time medial, bears the trochanter at its base.
This trochanter is clearly detached and directly follows the anterior surface of the bone; on the medial surface, the neck is rather deeply excavated between the trochanter and the portion that supports the head, whereas on the lateral surface it is nearly on the same plane as the lateral surface of the shaft of the femur.
The second trochanter is situated very high, as is seen in Buckland’s megalosaur; the base is extended and reaches to the level of the beginning of the greater trochanter.
Regarding the shaft of the bone itself, the anterior surface, rounded in its superior part, is flattened at the same time as it is widened; distally, it presents a furrow that separates the two condyles. The medial surface, which merges with the anterior surface proximally, is clearly distinct distally and separated from the anterior surface by a salient crest, at the end of which is the inferior trochanter. The posterior surface, flattened proximally, is rounded distally.
As I have said, the distal end presents two condyles separated from the patellar side by a groove that is less pronounced than the groove on the popliteal side. The medial condyle protrudes a little more than the lateral; opposite to that seen in Buckland’s megalosaur, in which the medial condyle is much more salient posteriorly than the lateral, in Megalosaurus superbus the two condyles are on the same plane posteriorly. The medial condyle is rounded anteroposteriorly and laterally compressed; the lateral condyle, larger than the other, is composed of two parts, one anterior and rounded, the other posterior and detached from the rest of the bone as a wide process; this arrangement is seen in Megalosaurus bucklandi.
Mr. Pierson’s collection includes the distal end of the femur of another individual showing that the megalosaur from the phosphates reached entirely as gigantic a size as the megalosaur from the Great Oolite. This femoral end is 0.470 m in circumference at the level of the condyles, and 0.033 m in circumference at the shaft of the bone; the lateral condyle is 0.145 m long anteroposteriorly, the medial condyle 0.135 m; at 0.220 m from the distal end, the bone still has a circumference of 0.265 m, with diameters of 0.095 m and 0.085 m; its cross-section at this point is prismatic. The anterior surface is separated from the medial surface by a strongly salient crest, whereas on the lateral side the anterior surface merges little by little with the lateral surface along a rounded edge. This surface shows a large furrow in its posterior and distal part that separates the lateral surface from the lateral condyle. The distal part of the posterior surface presents a deep depression for receiving the popliteal crest. Just as for the femur described above, the two condyles are seen to extend posteriorly to the same level, so that this character is not due to age; the groove separating these two condyles posteriorly is narrower, but relatively deeper, than in Buckland’s megalosaur.
Regarding the upper or proximal part, the megalosaur femur is more similar to that of saurians than crocodilians. In the saurians I used for comparison (Lacerta ocellata, Plestiodon pavimentatum, etc.), just as in the megalosaur, the femoral neck is directly on the extension of the posterior surface of the shaft, and forms a head slightly detached from the bone; the upper trochanter is separated from the articular head by a rather large and deep notch, with a furrow existing on the anteromedial surface between these two parts. Moreover the orientation of the trochanter is different; whereas this trochanter is anteriorly directed in the megalosaur, it is lateral in saurians. In crocodilians the proximal part of the femur is very different. Saurians lack a second trochanter, which exists in the megalosaur.
In the latter, the shaft of the bone does not present the double curvature seen in crocodilians and also in saurians, although less pronounced; in this regard, the megalosaur femur resembles that of birds.
The distal end resembles that of crocodilians.
(Pl. III, fig. 1.)
The tibia, of which only the proximal end is known, is rather similar to that of Megalosaurus bucklandi. This bone is 0.120 m wide near the proximal end. The femoral surface has the form of a curvilinear triangle; the anterior edge is convex, and the posterior edge is concave, above all medially; the articular surface with the fibula is in the form of a rather deep notch. The anterior edge of the femoral surface is straighter than in Buckland’s megalosaur; the marked crest that traverses the posterior surface of the bone in this latter species is also seen in Megalosaurus superbus; the part situated medial to this crest is strongly excavated, the lateral part being rounded (fig. 1, a).
(Pl. I, fig. 2.)
Two distal ends of this bone are known.
At the distal end, the lateral surface is convex, and the medial surface concave near the articular surface, where the bone is dilated; thus at 0.140 from at the articular end, the shaft of the bone is only 0.035 m wide, whereas it attains 0.080 m near the distal part. The articular end itself is rather different from that seen in Iguanodon; this surface is narrower, longer, and presents a series of small bumps; on the lateral edge grooves are seen going up for a length of around two centimeters on the shaft of the bone, grooves having to give passage to powerful tendons.
Metatarsals. — Although the bone figured under no. 3 in plate I is more slender and more elongated than the metatarsal of Buckland’s megalosaur figured by Phillips1, and resembles more the metatarsal of crocodilians, and the articular surface has much resemblance with those of animals from this latter group, the general analogies are rather with the megalosaurs, above all those offered for the proximal articular surface.
This metatarsal is slender and elongate; its length being 0.230 m, the width of the proximal face is 0.055 m, the length is 0.038 m; the distal surface is 0.045 m at its greatest width and 0.055 m at its greatest length. The shaft of the bone is cylindrical, the surfaces being rounded. The bone is dilated at its proximal end, the articular surface having the form of an irregular triangle whose peak is directed medially; the medial edge is straight, with several grooves that are continued on the ventral surface and are destined for the passage of tendons; the dorsal edge is rounded and continued by a regular curve with the lateral edge; the medial part is extended in a kind of beak, hollowed dorsally by a groove destined for one of the tendons going to the digits (Pl. I, fig. 3 b).
Whereas the proximal face is flat, or a little concave, the distal face is inflated and convex. A wide and deep fossa is visible at the end of the dorsal surface, similar to that in crocodilians; the lateral surface is regularly rounded; the ventral surface presents a similar fossa to that on the dorsal surface; a still larger fossa starts the medial edge and must lodge a sesamoid bone (Pl. I, Fig. 3 c).
If, as everyone supposes, the megalosaur had digits armed with strong claws, the form of the distal end of the metatarsal must be singularly favorable for wide dorsoventral movements of the digit.
Mr. Péron communicated to me the distal end of a metatarsal found at Grandpré (Ardennes) and indicating an animal of larger size. Indeed, the dorsoventral diameter of the articular end is 0.055 m. The bone is hollowed by a wide medullary cavity.
Mr. Péron recovered in the same locality a fragment of bone 0.090 m long that I am disposed to regard as the proximal end of a metatarsal or an lateral metacarpal. The lateral surface is flat, like the medial surface. The dorsal surface is rounded slightly to be connected with the lateral surface. The articular surface much resembles that figured in the diagram given by Phillips (Op. cit., p. 215, fig. 3); it is slightly concave; the medial and ventral edges are straight; the dorsal edge is rounded to rejoin the lateral edge; this surface is 0.045 m tall and 0.042 m at its greatest width (Pl. III, fig. 2).
Cuboid. (Pl. II, fig. 2). — The affinities between the megalosaur and crocodilians being great for the metatarsal bone, it is necessary regard the bone figured under no. 2 of plate II as a right cuboid*. In crocodilians, this bone articulates with the third and fourth metatarsals, whereas in a dinosaur from the scelidosaurid family, Scelidosaurus harrisonii1 from the Liassic, the astragalus, which is very large, contacts the second and third digits2. If our manner of seeing is exact, in the megalosaur the cuboid articulates only with a single digit, probably the fourth, the astragalus being in contact with nearly the entire proximal surface of the metatarsals.
The cuboid is large, being 0.055 m wide, 0.045 m in maximum height, and 0.030 m in maximum length.
The surface in contact with the metatarsal is sensibly flat and must be separated from this bone by a relatively thin cartilage. The posterior surface presents, in its median part, a strong crest directed in the direction of its height; this crest separates two concave surfaces, the lateral wider than the other, so that the astragalus must have the same form as in the crocodile, at least in its cuboidal portion. The dorsal surface (fig. 2 a.) of the cuboid is regularly rounded, the ventral surface rather deeply excavated; the anteromedial edge is itself indented to deliver passage to tendons whose mark is seen on the proximal part of the ventral surface of the metatarsal.
Phalanges. — The phalanx figured under no. 3 of plate IV (Bar-le-Duc; Pierson collection) comes from a large individual; indeed, it is 0.100 m long, 0.052 m wide at its distal end, and 0.056 m at its proximal end. It is excavated and transversely oval (fig. 3 a.). The distal end, also slightly transversely oval, is rounded in the form of a pulley (fig. 3, b). The dorsal surface is rounded, and the ventral surface slightly excavated anteroposteriorly; the lateral surfaces are slightly indented. Just as in the crocodile, a deep oval fossa is seen at the end of the lateral edge and near the distal surface. This phalanx, which resembles that of the scelidosaur in its shape, is less robust and more elongated; it does not present the two lateral expansions that are seen near the distal end in this animal.
Another phalanx 0.065 m long was found my Mr. Pierson. This completely preserved phalanx resembles those figured by Phillips (Op. cit., p. 286). The strongly concave posterior articular end is slightly oval. The ventral surface of the bone, flat proximally, is slightly convex along the rest of its extent. The dorsal surface is convex and merges with the lateral surfaces; a depression exists near the distal end.
It is probably necessary to regard the bone figured under no. 4 of plate IV as coming from a young individual. This bone is 0.030 m long. The proximal surface, sensibly quadrilateral in form, is concave; the ventral edge, longer than the rounded dorsal edge, is slightly notched in its median part. The distal articular surface is convex. The lateral surface is flat, the medial surface excavated near the distal end.
(Pl. II, fig. 6.)
Mantell described under the name Hylaeosaurus armatus1 a dinosaur from the Wealden whose skin was covered by bony, non-overlapping plates.
One of these plates was recovered by Mr. Ch. Barrois in the Ammonites mammillaris zone of Grandpré, and it entirely resembles that figured by Mantell under nos. 3 and 4 of plate X of his Memoir. This plates is 0.009 m and 0.011 m wide, oval, and elevated in its center into a sharp point.
(Pl. III, fig. 4, 5; Pl. IV, fig. 5)
With the bones of the megalosaur described above (vertebrae, femur, manus), Mr. Pierson found four vertebrae and two long bone fragments that cannot be referred to the megalosaur.
Indeed, among them the dorsal vertebrae have slightly concave articular surfaces. In contrast, the vertebrae of which I speak have a strongly concave anterior articular surface, and a convex posterior articular surface; these vertebrae are strongly deformed by fossilization.
One of these vertebrae (Pl. IV, fig. 5) is 0.060 m long. The lateral surfaces and the ventral surface are slightly excavated longitudinally. The posterior surface is convex and rounded. The articular processes, thrown posteriorly, are relatively robust and are detached in the form of a pyramid whose base is turned posteriorly; their lateral surface is flat, the ventral surface slightly excavated longitudinally.
These vertebrae recall those of pythonomorphs and still more those of crocodilians, more especially because the two fragments of bone remaining to be discussed are of this last type.
One of these bones (Pl. III, fig. 4) is the proximal part of a femur. This end is 0.065 m wide. The head is well developed and rounded. The entire anterior surface is rounded, however slightly depressed toward the medial edge; the posterior surface is rounded along the lateral edge, with which it merges insensibly, and is excavated along the medial edge.
The other fragment of bone (Pl. III, fig. 5, 5a), 0.100 m long, is the distal part of a tibia; the articular and is 0.080 m wide. The proximally rounded medial edge becomes trenchant toward the malleolus; the lateral edge is thin and trenchant along its entire length. The distal articular surface (Pl. III, fig. 7a) has greater similarities with that of the crocodile.
(Pl. II, fig. 11.)
I refer to this genus a tooth recovered by Mr. Péron in the greensands of Grandpré. This tooth, which would be around 0.033 m long if it were intact, is massive and recurved toward the medial surface; the two strongly bent surfaces are separated by a salient carina that reigns along the entire length; this carina is not serrated, but it is noted that the tooth which I studied is slightly eroded; in Dacosaurus, the fine and serrated denticles of the salient edge are very faint, and are seen only on teeth in a state of perfect preservation. The cross-section of the tooth is circular at the base and elliptical toward the apex. The enamel is ornamented with numerous fine folds, between which are seen very fine, numerous and irregular striations that make the enamel appear like chagrine under the magnifying glass.
The mosasaurid family, appearing in the Upper Jurassic period with the dacosaur genus (Dacosaurus maximus, Plien.; D. pimaevus, Sauvg.), is continued into the Cretaceous of Europe by the genera Liodon and Mosasaurus; it is interesting to recover a dacosaur near the base of the Cretaceous terrains1.
ICHTHYOSAURUS CAMPYLODON Carter.
(Pl. II, fig. 12; Pl. IV, fig. 6, 7.)
This species, studied by Messrs. Carter2 and Owen3, was recovered in France by Mr. Barrois in the Ammonites mammillaris zone of Grandpré, Louppy (Meuse), and Villotte, where it seems to be common; indeed, Mr. Barrois recovered no fewer than 70 vertebrae at Grandpré; I. campylodon is equally abundant in the Cretaceous of England, from the Lower Greensand (lower Gault) up to the glauconitic Cretaceous of Douvres with Holaster subglobosus1. It is found in the phosphatic chalk beds of Boulogne-sur-Mer and in the Ammonites mammillaris zone of Bar-le-Duc.
Among the recovered elements in this latter locality, I only will mention several vertebrae.
A posterior cervical vertebra is 0.037 m long and 0.060 m tall, the articular surface having 0.060 m (length 100; height 156; width 159). The dorsal surface is sensible flat, the medullary canal being wide; the dorsal edge is nearly straight. The lateral edges are rounded in a regular curve, so that to be strictly accurate there is not a ventral surface. The two articular tubercles for the rib, situated very close to one another, are placed in contact with the anterior edge.
This vertebra is remarkable for its length compared to the two diameters, so that it is still thicker than the vertebrae of Ichthyosaurus thyreospondylus Ow. from the Kimmeridgian.
Anterior dorsal vertebrae. — The length of one of these vertebrae is 0.036 m, its height is 0.080 m, and its width is 0.076 m (length 100; height 222; width 214). The same character of massiveness is found on this vertebra. The dorsal surface is excavated. The two lateral edges are reunited by a regular curve; the largest width of the articular surface is found toward the middle of the height. The dorsal articular tubercle for the rib is placed very high, toward the limit of the upper quarter of the centrum height, very near the anterior edge; the ventral tubercle, situated nearly at the mid-height of centrum, is a little posterior to the dorsal tubercle.
Middle dorsal vertebrae. — The two costal tubercles are moved back, the anterior tubercle being sensibly at the level of mid-height, very near the anterior edge; the very strong posterior tubercle is placed a little posteriorly.
Posterior dorsal vertebrae. — These vertebrae are elongated transversely; the dorsal surface is nearly flat, just as the ventral face. Length 0.025 m; height 0.070 m; width 0.085 m (length 100; height 280; width 340).
Lumbar vertebrae. — A lumbar vertebra recovered at Grandpré (Ardennes) has similar dimensions: length 0.042 m; height 0.112 m; width 0.115 m (length 100; height 266; width 274). The dorsal half of the centrum is triangular, the dorsal surface being entirely flat; the ventral half is rounded. The rib attachments are placed very low and close together.
Anterior caudal vertebrae. — These vertebrae have a slightly triangular shape, like that of I. thyreospondylus from the Kimmeridgian terrain; the ventral edge is slightly rounded. Length 0.040 m; height 0.100 m; width 0.155 m (length 100; height 250; width 287).
Posterior caudal vertebrae. — Numerous caudals recovered at Grandpré come from the posterior part of the body; indeed, certain of these vertebrae are only 0.005 m tall; the articular surfaces are circular.
Humerus. — A humerus, found in the Ammonites mammillaris zone of Grandpré and forming part of the collection of the Faculty of Sciences of Lille, indicates an animal of large size; indeed, it is 0.160 m long with a maximum thickness of 0.125 m in the proximal part. The articular head is large and rounded, with a slightly transversely oval shape. A crest that rises toward mid-length of the bone makes the lateral part of the humeral head move medially. The lateral surface of the humeral shaft is slightly concave for its whole length, and more excavated toward the distal part; the strongly excavated anterior surface merges little by little with the equally concave medial surface, like the posterior surface. The distal end, slightly convex on the whole, is divided by a weakly marked crest into two parts, moving in opposite directions and serving for the articulation of the forearm bones; this surface is rugose (Pl. IV, fig. 7).
Teeth. — Some teeth similar to those figured by Mr. Owen were recovered in the greensands of Grandpré (collection of the Faculty of Sciences of Lille; Péron collection). One of these teeth is 0.056 m long, the enameled portion is only 0.020 m long. The square base is strong. The enameled part is ornamented with large striations going all the way to the apex; the enamel is reticulated like chagrine, as much on the striations as between them (Pl. II, fig. 12).
Quadrate. — By analogy with an element preserved in the Musée de Boulogne-sur-Mer, and determined by Professor Seeley to be a quadrate of the ichthyosaur, I consider the bone represented under no. 6 of plate IV as the quadrate of Ichthyosaurus campylodon, the only ichthyosaur yet known in the Gault of the northeastern Paris Basin.
This bone is remarkably robust, although certainly incomplete; it measures 0.100 m tall and 0.114 m wide at its ventral end.
The ventral surface contacting the mandible is very thick (0.095 m), above all in its median part, and rounded principally in the lateral part, which is irregular and presents crevices and hunchbacked portions; this surface is decomposed into two portions with opposite inclinations, one from dorsal to ventral and from lateral to medial, the other from medial to lateral. In crocodiles and turtles, the articular surface with the mandible is entirely concave; in pythonomorphs (Mosasaurus, Platecarpus) this surface is convex1; it is the same in the ichthyosaur.
The lateral surface can equally be divided into two portions: one, turned directly laterally, is regularly convex and it is at this level that the bone is thickest; the other, directed posteriorly, is noticeably flat. The medial surface is flat, slightly concave even close to the marked angle that forms the lateral and ventral part of the bone. Above this angle the lateral edge presents a wide surface for articulation with the temporal. The medial edge is relatively thin.
It is known that in the crocodile, the tympanic bone is extended into a process that skirts the temporal scales and forms the lateral part of the auditory canal. In sea turtles, this extension, much shorter and differently shaped, has the same connections; it forms a veritable box, from whose ventral part is detached a strong, downward-directed process for the articulation with the lower jaw.
If it is so in the ichthyosaur as in the turtle and crocodile, in the figured bone I would have only the mandibular portion of the quadrate, which in the sea turtle, for example, forms the large articular process. It has been known since Cuvier that “the tympanic bone of saurians, nearly always reduced into a prismatic stem, is not connected with the other bones to form part of the solid envelope of the head, and seems in the skeleton to be only a pedicle for the lower jaw.1” It could not be the same in the ichthyosaur. Indeed, in this latter, “which is characteristic posterior to the orbit and distinguishes it from lizards, this is a wide bone that articulates with the posterior edge of the posterior frontal and the jugal, and goes at its other end to take part in the articular surface that bears the lower jaw. The bone that provides the rest of this articular surface is placed more medially than the preceding one, and is suspended by the mastoid and lateral occipital.2” Consequently, the connections in the ichthyosaur are those seen in the crocodile.
PLESIOSAURUS PACHYOMUS Owen3.
P. pachyomus, from the glauconitic chalk with Ammonites inflatus (Upper Greensand) of Cambridge and the lower Gault (Lower Greensand) of the Isle of Wight, was found by Mr. Ch. Barrois in the Ammonites mammillaris greensands of Grandpré (Ardennes).
The cervical vertebrae found in this locality greatly resemble the corresponding vertebrae of P. carinatus Ow. from the upper part of the Jurassic terrains. The vertebra is short, the height being much greater than the length. The articular surfaces, thick around their circumference, are deeply excavated in their central part; the dorsal edge is nearly straight. The ventral surface presents a salient carina, on each side of which are two deep foramina for vessels; this surface is very straight, such that the contour of the articular surface is triangular ventrally. The attachment surface for the rib is very large and oval, occupying nearly the entire length of the lateral surface and most of its height. The suture that delimits the neural arch is only separated from this articular surface by a weak interval. The base of the neural arch is wide. The length being equal to 100, the height is 175, the width 168.
An anterior dorsal vertebra similarly has a length of 0.034 m, height 0.055 m, and width 0.037 m (length 100; height 161; width 167). The greatest width of the articular surface is reported toward the top. On the ventral surface is a sharp carina, on each side of which are vascular foramina. The attachment surface for the neurapophysis is wide and descends low on the lateral surfaces; the part of this attachment seen on the dorsal surface is wide and very deep.
PLESIOSAURUS LATISPINUS Owen.
This species, described by Mr. Owen1, differs from P. pachyomus by the great length and width of the centrum relative to the height, the smaller and more prominent costal surface, and the thinner edge of the articular surface.
Noted in the glauconitic chalk with Ammonites inflatus (Upper Greensand) of Cambridge, besides in the lower Gault (Lower Greensand) of the Isle of Wight, Plesiosaurus latispinus was found by Mr. Ch. Barrois in the Ammonites mammillaris greensands of Grandpré in the Ardennes, and by Mr. L. Pierson in the environs of Bar-le-Duc.
A cervical vertebra coming from this last locality entirely resembles the vertebra figured by Mr. Owen under no. 2 of plate VII, and indicates a species of large size; indeed, the length of the centrum is 0.080 m, the height of the articular surface is 0.078 m, and its width is 0.092 m (length 100; height 98; width 115). The articular surfaces, a little oblong transversely, are hardly excavated and slightly prominent in the middle; the edge is a little thick. The ventral surface, hardly excavated longitudinally, bears a wide but hardly salient carina, on each side of which is seen a rather wide vascular foramen; the surface is slightly concave between this carina and the attachment surface for the rib. Situated at the edge of the ventral and lateral surfaces, it is placed closer to the posterior edge than the anterior; it occupies only half of the length of the centrum; its form is oval. The lateral surfaces are slightly excavated anteroposteriorly. The base of the neural arch is wide.
Another cervical vertebra comes from the Ammonites mammillaris beds of Louppy (Meuse), forming part of the collection of the Faculty of Sciences of Lille. This vertebra is 0.067 m long, the articular surfaces being 0.056 m tall with a bi-transverse diameter of 0.068 m (length 100; height 95; width 101). The transversely oval articular surfaces are flat. The ventral surface bears a salient carina on each side of which the surface is slightly excavated up to the print for the rib. This print, situated at nearly an equal distance from the anterior and posterior edges, is oval and occupies nearly the length of the centrum.
PLESIOSAURUS PLANUS, Owen1.
Plesiosaurus planus, from the Upper Greensand of Cambridge, is characterized by flattening of the articular surfaces; the vertebrae are short and indicate a small-sized species; the costal surfaces are straight and oblong; the neural surface is extended toward the posterior part of the centrum; the neurapophyseal surfaces, of the same size anteriorly, are smooth and hardly deep, their contour being saddle-shaped; the flattening of the terminal surfaces is remarkable and indicates weak movements of the neck.
In the mid-dorsal vertebrae the dorsoventral diameter of the centrum increases at the expense of the transverse diameter; the articular surface is weakly concave, with a slight elevation at its middle. In the tail the vertebrae are short and massive; the articular surfaces are more excavated than in the other vertebrae.
P. planus was found in the Cretaceous phosphates of Bar-le-Duc. One vertebrae is 0.040 m long, 0.060 m tall, and 0.077 m wide (length 100; height 150; width 192). This species was also recovered by Mr. Ch. Barrois in the Am. mammillaris zone of Grandpré, in the Ardennes.
The genus Polycotylus, established by Mr. Cope1, was represented only by one species in the Cretaceous of America, when I made known under the name Polycotylus suprajurensis2 another species established on a humerus recovered in the upper Kimmeridgian beds of Boulogne-sur-Mer.
I believe that a fragment of another humerus found by Mr. Ch. Barrois in the Gault with Ammonites milletianus of Grandpré (Ardennes) should be referred to the same genus. The articular head of this bone much resembles that of Polycotylus suprajurensis; the glenoid part is entirely smoother and presents a sort of salient crest that divides it in two; the contours of this part are also different. The fragment that I figured in the Bulletins of the Geological Society3 certainly indicates a species distinct from those of the Cretaceous of America and the Upper Jurassic of Boulogne-sur-Mer; it is desirable that the discovery of better-preserved bones would make more completely known this still poorly defined genus in the Cretaceous of Europe.
POLYPTYCHODON INTERRUPTUS Owen
(Pl. II, fig. 9, 10, 11.)
Under the name Polyptychodon, Mr. Richard Owen established in 18414 a genus for reptiles of uncertain placement, characterized by strongly grooved teeth; this genus was found in the lower beds of the Cretaceous terrain of England. Later, Mr. Owen made known that the teeth were implanted in distinct alveoli, as in crocodiles.5 Some more recent discoveries, made in the Lower Greensand of Kent county, showed that the skull, pubis, ischium, and vertebrae brought this genus closer to the plesiosaur type; also, although the ends of the limbs are still unknown, Mr. Owen placed it in the order Sauropterygia. Mr. Seeley finally studied the same genus.
Two species are admitted by Mr. Owen according to the teeth, Polyptychodon continuus from the Lower Greensand, and Polyptychodon interruptus from the Upper Greensand; this species was found in the Cretaceous of Lewes.
Polyptychodon interruptus was recovered in France by Mr. Charles Barrois in the Gault with Ammonites mammillaris of Grandpré and Louppy in the Ardennes, and by Mr. Pierson in the Ammonites mammillaris beds of Bar-le-Duc; it was also noted at Boulogne-sur-Mer in the same beds.
The Meuse provided the very well-preserved tooth that I figure. This tooth is 0.125 m long, the enameled part being 0.095 m; the crown is noticeably circular. The external face bears only five or six strong salient ribs, of which three are continued up to the apex; between these ribs the enameled surface is vermiculate. The internal face is ornamented with about fifty strong, numerous striations, of which twenty are extended to the apex of the crown; between these principal striations are others that are elevated in general up to a little more than half the height of the tooth, whereas others are only continued a brief distance. The thickness of the tooth at the base of the enameled portion is 0.040 m, the full part being only 0.004 m thick; indeed, at the base of the tooth exists a wide, cone-shaped pulp cavity, 0.030 m wide; toward the upper third of the tooth, the thickness of which is 0.030 m, the width of the pulp cavity is only 0.006 m; still higher, this width is reduced to 0.005 m; the cavity disappears toward the apex (Pl. II, fig. 9).
The ornamentation of the tooth differs according to the place that it occupies in the jaw; thus I was able to study a tooth that on the external face bears more numerous striations than on the tooth described above. It is the same for two small teeth that were conveyed to me by Mr. Péron.
The tooth figured under no. 10 of plate II is without doubt an anterior tooth; it is recurved toward the internal face, which is thus ornamented as I said; on the external face the striations are stronger and more numerous than on the typical tooth described above. Finally, these striations are quite as numerous on the external face as on the internal face of a tooth (fig. 11) that seems to fall between Polyptychodon interruptus and Polyptychodon continuus, such that I have strong doubts as to the validity of this latter species, established without doubt on teeth from the anterior part of the jaws.
The teeth figured were recovered by Mr. Péron in the Am. mammillaris zone of Grandpré; Mr. Barrois found the species at Villotte (Meuse).