SKULLS OP CYNODONT REPTILES. 



901 



supposed perforation in the zygomatic arch is, in my opinion, not 

 a natural feature and has been produced post mortem. The side 

 view which I give of the skull of C. plojtycejjs is fairly similar, 

 except that the skull is here much broader and flatter, and in 

 this species, at least, there is no trace of an opening in the 

 zygoma. 



The snout of CynognatJms differs from that of Bauria and 

 Nythoscmrus chiefly in the fact that the septomaxillaiy does not 

 appear on the face, though it can be readily seen within the 

 nostril. 



Text-fig. 171. 



Side view of tlie skull of Ctjnngnathus platj/ceps. With the exception of the 

 front of the snout the drawing is made from the vevy tine type skull in the 

 Albany Museum. Tlie front of the snout is from the specimen described by 

 Seeley as ? Cynognathiis le^itorhinus. As I showed some years ago, this is 

 unquestionably the snout of a nearly full-grown specimen of Cynognatlius 

 platyoeps. 



The premaxilla is relatively rather larger than in NytJiosaurus, 

 while the maxilla is about equally well developed in the two 

 genera. The canine is, however, much further forward in Cyno- 

 ynathii,s than in the smaller genus. 



The nasal bone is fairly similar in the two genera, being broad 

 both in front and behind and narrow in the middle. 



The lachrymal extends further forward than in Nyihosaurus, 

 the portion showing on the face being nearly as large as the 

 orbit. 



The prefrontal is a long narrow bone which forms the greater 

 part of the upper margin of the orbit, and by meeting with the 

 postorbital completely shuts out the frontal from the orbital 

 margin. 



The frontals are each about four times as long as broad. 

 In front they meet the nasals. Laterally they are in contact 

 with the prefrontals and postorbitals. Posteriorly they taper 

 away to narrow points, wliich meet the anterior ends of the 

 parietals. 



The postorbital is a large triangular bone. In front it meets 

 Pkoc. Zool. Soc— 1911, No. LXII. 62 



