380 Transactions of the South African Philosophical Society. 



backwards, and the apices of the four following the first are 

 situated at the following distances from the apex of the first — 

 1*4, 2-9, 4-9, and 7 mm. respectively. The fourth tooth measures 

 2 mm. in length and 1-2 mm. in height ; the fifth is 2 mm. in length 

 and 1*5 mm. in height. Below the fourth and fifth teeth the jaw 

 becomes much deeper than elsewhere, measuring 3 mm. Behind 

 the fifth tooth is a smaller sixth tooth which is not very satisfactorly 

 displayed but which is distinctly acrodont, showing that the jaw 

 is probably that of an adult animal. Along the jaw, at a distance of 

 1 mm. from the base of the teeth, runs a low, longitudinal ridge 

 probably for the attachment of the lip. At the posterior part of the 

 specimen, the dentary passes upwards and curves very markedly 

 inwards. There is no part of a coronoid bone preserved. From the 

 shape of the back part of the dentary it seems probable that the 

 planes of the two jaws sloped markedly inwards. 



It is impossible from so small a fragment to say much of the 

 animal, but it was evidently a form about half the size of Sphenodon 

 and with much more slender jaws. 



The deposit from which the specimen was obtained is a bone bed 

 containing many fragments of bones and teeth, and it is possible 

 that Mr. Brown's industry may yet be rewarded by other fragments 

 which can be recognised as belonging to Palacrodon. 



The specimen is of interest as being the earliest known true 

 Ehynchocephalian. The Order Ehynchocephalia, which was 

 formed for the reception of reptiles allied to Sphenodon, has 

 been held by many to include the primitive types such as 

 Palceohatteria, Rliynchosanrus , Hyperodapedon, and a number of 

 others. By other authors it is held that if the order is expanded 

 sufficiently to include the early types with plate-like pelvis, it 

 becomes exceedingly difficult to define it and much confusion is 

 likely to arise in forming the limits of the group. Following most 

 American authorities I consider it advisable to restrict the group to 

 those forms with two temporal arches and radiating pelvis — the 

 Ehynchocephalia vera of others. This restricted group has hitherto 

 not been known earlier than the Jurassic, but it might have been 

 inferred to have originated in the Triassic. Our rich South African 

 Triassic deposits will probably yield other types that will throw light 

 on the origin of the group. 



