292 PROSAURIA CHAP. VIII 



sacrals and more than thirty caudals, some of which liave liifur- 

 cated spinous processes. 



Sub-Order 2. Rhynchocephali. — The ventral pelvic liones 

 resemble those of lizards and enclose a wide pubo-ischiadic foramen. 

 There are only two sacral vertebrae. The abdominal ribs are 

 closely packed, each transverse set consisting of only three rod- 

 shaped pieces instead of many small oat-shaped nodnles. The 

 intercentra are sometimes suppressed in the trunk-region. 



Rhyncliosaurus from the Upper Trias of Warwickshire and 

 Shropshire, and Hyperod((j>edon of the same age, found at Elgin, 

 in Warwickshire, and also in Central India, are rather large, H. 

 fjordoni measuring 6 feet in length. Both have a short, broad, 

 and stout cranium, and curved down, toothless premaxillae, 

 hence the name Ehynchocephali ; the nares are confluent ; the 

 teeth are numerous and small, and are liable to be worn down 

 so that the animals ultimately bite with the edges of the jaws, 

 to which the teeth are ankylosed. The premaxillaries of 

 Bhynchosaurus are curved downwards over a slightly upcurved, 

 likewise toothless process of the mandibles, which form a strong 

 symphysis. All the teeth are very small, absent, or minute on the 

 mandibles, forming one series on tlie maxillae, several rows on 

 the vomers and especially on the palatines, which latter remain 

 separated from each other. Hyperodapedon seems to have lost 

 the intercentra ; its vertebrae are solid, those of the neck are 

 opisthocoelous. The interparietal foramen is likewise al^olished. 

 The hook-shaped end of the curved-down premaxillae fits into a 

 bifurcation of the mandibles in front of their stout symphysis. 

 The teeth are similar to those of the other genus. Whilst these, 

 the earliest known genera of Rhynchocephali, are already in 

 various ways rather specialised, e.g. the hooked beak and the loss 

 of the intercentra, the two following fossil genera, although of 

 much later date, namely Upper Triassic, are more closely allied to 

 the recent Sphenodon. 



Homocmaurus pidchellus and other species in Germany are only 

 () to 8 inches long. The vertebral column consists of twenty- 

 three presacral and many caudal vertebrae. The first five 

 cervicals are devoid ol" ril)S. Intercentra are restricted to the 

 neck and the anterior portion of the tail. The mandibles are 

 not fused together. The nares are divided by a bony sei»tum. 

 Each premaxillary has one rathc^r broad tooth. The teeth of 



