358 LIEUT. R. BROOM ON 



I'elative proportions of the parts diiFer very considerably from 

 those of the type species. 



In the lower jaw there appears to be a series of 6 teeth with 

 some replacing ones. 



Seeing that Owen's specimen caine from the same locality as 

 Huxley's I was inclined to regard them as belonging to the same 

 species, but the differences in proportions appear to be sufficiently 

 great to warrant us at least provisionally in regarding them as 

 distinct. 



Pristerodon agilis (Broom). 



In 1904 I described, in the Records of the Albany Museum, 

 the skull of a small Anomodont found by me at Pearston. At 

 that time it was not known that Oudenodon is the female of 

 Dicynodon, and as the Capetown specimen of Fristerodon mckayi 

 is tusked, and the new allied form which I discovered being 

 tuskless, I placed it in a new genus and called it Opisthoctenodon 

 agilis. As, however, the tusk is now known to be a sexual 

 character, this species must be placed in Huxley's genus 

 Fristerodon. 



The skull is much smaller than in F. mckayi and narrower 

 relatively, but in most characters it agrees closely, and the molars 

 are very similar. 



Fristerodon mckayi and F. ranicej^s both come from the 

 Pareiasaurus zone, but P. agilis is from the Endotliiodon zone. 



Pristerodon brachyops (Broom). 



This species when described was also placed in the genus 

 Opisthoctenodon. As the crowns of the molars are unknown it is 

 impossible to be certain that it belongs to Fristerodon^ but it 

 agrees sufficiently to admit of its being placed here, at least 

 provisionally. It is probably from the C LStecephalus zone. 



Tropidostoma microtrema (Seeley). (Text-figs. 3 k 4.) 



In 1889 Seeley described an Anomodont occiput under 

 the name Dicynodon microtrema. The occiput formed part 

 of Mr. T. Bain's collection and was obtained, according to 

 Mr. Watson, on the farm Tafelberg, in the Beaufort West 

 district. In the British Museum there is a good series of 

 Dicynodont skull-remains from the same locality, and the 

 majority belong, I think there is little doubt, to the one species. 

 Fortunately there are a number of snouts and a few mandibles. 

 Both tusked males and tuskless females are represented, and 

 most specimens show evidence of small molars behind the tusk, 

 or caniniform process. The specimens diflter considerably in size, 

 doubtless due to difference in age, and the differences in dentition 

 are probably due to the same factor. There appear to be 

 normally four molars, but as age advances they become reduced 

 to three, two, or one, and in old age get comislctely lost. 



