96 BR. n. BROOM ox THE [Feb. 7, 



6. On Rome Points in the Anatomy of the Tlieriodont Reptile 

 Diademodon. By R. Broobi, M.D., C.M.Z.S., Victoria 



College^ Stell(mboscli. 



[Received December 29, 1904.] 

 (Plate X.*) 



Mr. Alfred Brown, of Aliwal Noi'tli, to whom science already 

 owes so much, has recently made another discovery of considerable 

 importance. In the neighbourhood of Aliwal he has found a very 

 well-preserved Theriodont mandible with a number of other well- 

 preserved bones, all belonging to the same individual ; and these 

 he has kindly forwarded to me for examination and description. 

 "When the remains were fully developed it was found that we had 

 two dentaries, two ilia, two ischia, a. pubis, a femur, and a lumbar 

 vertebra of Diademodon mastacus Seeley. Though the type 

 specimen consists of only a fragment of maxilla with some molar 

 teeth, the molars in the present mandible agree so closely in 

 structure and size as to leave little doubt that the remains are 

 those of D. mastacus. 



With the exception of the anterior pai't, both dentaries are well 

 preserved, the hinder part of the left being in almost perfect 

 condition. The symphysis is missing, but from the impression 

 left it is pi'etty manifest that the two dentaries have been 

 anchylosed in front. The dentary resembles that of Gomplio- 

 gnathus and Trira"hodon in the very great development of its 

 posterior portion. The coronoid process is of large size, but does 

 not terminate in a posteriorly directed point as in most mammals. 

 The posterior part of the dentary, as in Cynognathus, probably 

 almost reached the articulation, and apparently overlapped the 

 articular as in tire better known Theriodonts. A small but distinct 

 angle is formed, very similar to, but better developed than, that 

 in Trirashodon. 



Behind the canine there is a short diastema of about 10 mm., and 

 then a series of four teeth which may be i-egarded as premolars. 

 Behind the premolars are seven molars. 



The first premolar is smaller than the others, but is imperfectly 

 preserved. It probably, however, does not differ from the others 

 in structure. Each of the posterior of three premolars is a 

 rounded tooth in which the height is about twice as great as the 

 antero-posterior measurement. When viewed from the outer side, 

 each tooth appears to be a simple pointed cone, but in reality the 

 top is about as broad as the base, owing to there being on the 

 inside of the tooth a second cusp only a little shorter than the 

 outer. The outer cusp in the unworn condition is probably finely 

 serrated on both its anterior and posterior edges. The foui'th 



* For explanation of the Plate, see p. 102. 



