Sovie Neiv Primitive TJieriodonts. 151 



The specimen was presented to the museum by Mr. D. Arnot, and 

 was obtained at Colesberg. 



IcTIDOSAUKUS ANGUSTICEPS, g. et Sp. nov. 



The specimen which I have made the type of this new genus and 

 species is the imperfect snout with lower jaw of a medium-sized 

 reptile. The left side of the specimen is but imperfectly cleared of 

 the very hard matrix, and the right side is very badly weathered. 

 The weathering, however, has been the means of displaying prac- 

 tically the entire dentition of both jaws. The snout is considerably 

 deeper than broad, even when the effects of crushing are allowed 

 for ; and the nostrils are practically terminal. 



The nasal bones are fairly well preserved. Posteriorly they are 

 comparatively narrow, but become broader near the front end. The 

 general relations of the nasals to the maxillaries and premaxillaries 

 are very similar to those seen in Scylacosaurus. 



The premaxillary and maxillary bones so far as preserved differ 

 from those bones in Scylacosaurus only in being much deeper. 



The lower jaw is badly preserved. It is rather slender, but a little 

 behind the canine it is considerably deepened to accommodate the 

 large upper canine. 



The dentition resembles very considerably that of Scylacosaurus. 

 The incisors, however, are five in number, of which the first four are 

 of moderate size and the fifth small. In the maxillary there is a 

 large pointed canine with a serrated posterior border. In front of 

 this large canine and very close to it is a minute additional canine. 

 The small canine is the first of the maxillary teeth and is doubtless 

 the homologue of the first canine in Scylacosaurus, while the large 

 canine is no doubt the homologue of the second canine in that genus. 

 In the type specimen there is no evidence of a third canine, but in a 

 second very imperfect specimen, which undoubtedly belongs to the 

 same genus and most probably to the same species, there is evidence 

 of there having been another canine. The molars are probably 9 

 in number. Eight are undoubtedly present, but the last molar on the 

 left side, as judged by its distance from the canine, is most probably 

 a ninth. The molars are all comparatively small and subequal. In 

 the lower jaw there are three long pointed incisors, one large pointed 

 canine, and apparently 9 molars. The dental formula of Ictido- 

 saurus would thus appear to be : — 



.5 2 (or 3 ?) 9 ^ 32 ? 34 



