440 J. W. HULKE ON IGTJAN^ODON PEESTWICHH 



obviously much more lizard-like than crocodilian. The preponder- 

 ance of Lacertilian resemblance is not merely a superficial one ; it is 

 evident in many structural details. In the occiput the shape, so 

 far as is shown in this fossil (and in this it agrees with my Erooke 

 Iguanodon-skull), has certainly a greater resemblance to that of a 

 crocodile than lizard ; but this superficial likeness is outweighed by 

 the lizard-like entrance of the supraoccipital bone into the foramen 

 magnum, from which it is excluded in the crocodile. In the upper 

 surface of the skull the shape and size of the upper temporal open- 

 ings, the form of the parietal bone, the division of the frontal bone, 

 the large size and form of the nasal bones, are all lacertilian cor- 

 respondences. The form of the maxilla, the mode of articulation 

 of the mandible by a suspended quadrate not wedged into the side 

 of the skull, and the dentition are other lizard-resemblances. On 

 the under surface of the skull the downward extension of a median 

 process of the basioccipital bone is at first sight a crocodilian feature ; 

 but it differs from the crocodilian's basioccipital in direction aud 

 relations. However, whatever value may be attached to this super- 

 ficial similarity, it is more than balanced by the divided palate, 

 shown by the free exposure of the basioccipital and basisphenoid 

 bones throughout their whole extent, and by the absence from the 

 maxillse of any trace of palatal extension, or of attachment of thoso 

 bones which in the crocodile close the palate and separate the nasal 

 and buccal passages. 



Vertebral Column. — Sixty-four centra and a considerable number of 

 pieces of neural arch and processes give very complete information as 

 to the structure of every part of the vertebral column. Of the centra 

 25 are prassacral, 4 are sacral, and 35 are postsacral or caudal. 

 For convenience of reference, they have been consecutively numbered 

 in what appears to be their natural sequence in the column ; but 

 probably several are missing from in front and behind the sacrum. 



WecJc (PI. XIX. figs. 1-4). — Of the 25 prsesacral vertebras, 7 have, 

 either wholly upon the centrum, or jointly on this and on the arch, 

 an articular process for the attachment of the lower branch of a 

 forked riblet — a lower or capitular costal facet, parapophysis — which 

 stamps them cervical. Some are much crushed ; and in all the neural 

 arch is much mutilated. All are opisthocoelous, the posterior surface 

 cupped, the anterior convex. Both surfaces retain marks of a con- 

 centrically laminated intervertebral cartilage. The contour of the 

 anterior surface is almost a rhomb, in which the infero-lateral sides 

 include an angle of about 100° ; the upper angle is cut ofif by the 

 neural canal ; and the supero-lateral and infero-lateral sides include 

 an angle of about 80°. The horizontal exceeds the vertical diameter. 

 The lateral non-articular surfaces of the centrum are concave longi- 

 tudinally, and they are indented by a depression, which is deeper 

 towards the front. Below this depression the opposite sides of the 

 centrum meet in a median keel. The borders, where at each end 

 the sides and articular surfaces meet, and the keel are rugose in 

 all the cervical vertebrce, as in most of the succeeding praesacral 

 centra. 



