ON ANOMODONT EBPTILES. 355 



26. On the Anomodont Genera, Pristerodon and Tropido- 

 stoma. By Lieut. U. Broom, M.D., D.Sc, C.M.Z.S., 

 R.A.M.G. 



[Received April 27, 1915 : Read May 11, 1915.] 

 (Text-figures 1-4.) 



Index. 



Structure ; Systematic : Page 



Pristerodon mckayi 355 



F.raniceps 357 



P. agilis 358 



P. hrachynps 358 



Tropidostoma microtrema 358 



Pristerodon mckayi Huxley. (Text-fig. 1.) 



In 1868 Huxley described, under the name Pristerodon mckayi, 

 a fairly well-preserved skull of a small Anomodont reptile. 

 Almost the whole of the right side is shown in good condition, 

 and a considerable part of the leftside. There are also associated 

 with the specimen, besides the jaws belonging to the skull, a few 

 other mandibular remains. Huxley apparently believed the 

 animal to be a lizard, as he refers to the specimen as " a shattered 

 lacertilian skull, having very much the general shape of that of 

 Rhynchosaurus, being very broad posteriorly owing to the large 

 size of the supratemporal fossa, and tapering anteriorly." 



The skull when complete probably measured 87 mm. from 

 the snout to the transverse plane of the squamosals, and the 

 greatest breadth is about 70 mm. The interorbital measurement 

 is 17 mm., and the intertemporal measurement 18'5 mm. The 

 antero-posterior measurement of the orbit is 22 mm. In the 

 type-skull there is no tusk, the animal having been a female, but 

 a specimen in the South African Museum shows a Dicynodon- 

 like tusk. The maxilla and the mandible have each, as shown 

 by Huxley, a series of small teeth which have high crowns 

 i-emarkable for being smooth in front and having about. 8 or 9 

 relatively strong denticulations on the posterior side. The exact 

 number of teeth appears to vary with age, but in the type there 

 appear to be as many as 12 arranged somewhat irregularly and 

 one or two being probably replacing teeth. 



In structure the skull is typically Dicynodont. The frontals 

 are large and pass backwards between the postfrontals and 

 preparietal. The postfrontal is well developed, but in the 

 specimen it is difficult to be quite sure of the sutures of its 

 anterior and outer end, but. they are probably as I have figured 

 them, in dotted line. The poster bital is a larger bone which 

 forms most of the postorbital arch and the whole of the 

 inner border of the temporal fossa. The preparietal is long and 



