908 



DR. R. BROOM ON THE 



of a pin, and having similar relations to the stapes in Cyno- 

 gnathus. 



The occiput is not well known, but is apparently very similar 

 to that of Cynognathus. 



The lower jaw has a very large coronoirl process and a condylar 

 process which nearly reaches the articulation. The articular, 

 angular, and surangular are on the whole very similar to those of 

 Cynognathus. 



One of the most striking points of difference from Nythosaurii.8 

 and Cynognathus is in the structure of the molar teeth, which 

 have flattened tops, and the lower molars instead of passing inside 

 of them, as in these other genera, meet them much in the same 

 way as do the molars in Mammals. 



The dental formula is the same as in Cynognathus, viz. : 



• 41 9 



]. g, c. -^, m. ^. 



Diademodon and Gomjihognathus. 

 (PL XLYI. fig. 9, & text-figs. 175-178.) 



Diademodon resembles Gomjyhognathus so closely, differing only 

 in size and in the number of molars, that there is some reason for 

 suspecting that Diademodon may be an immatiu^e G mnphognathus. 

 If this turns out to be the case, the genus must take the earlier 

 name Diademodon. The following description of a skull is based 

 on a beautifully preserved skull in the British Museum, which 

 may be called Gomphognatlms minor ^ but which unfortunately has 

 lost the snout, on a fairly good skull of D. mastacus in the South 

 African Museum, on two other good skulls of Gomjjhognathus in 

 the British Museum, and on the type skull of Gomphognathus 

 kannemeyeri in the Albany Museum. As the result of the 

 examination of this very fine material, the Gomphognathus skull 

 is better known even than that of Cynognathus, and almost as 

 well as that of the living Ornithorhynchiis. 



The premaxilla is fairly large, but, as in all other Cjmodonts, 

 considerably overlapped by the front of the maxilla. It has a 

 strong internasal process, and forms the anterior and most of the 

 lower border of the nostril. It has a very considerable palatal 

 development, the two bones meeting in the middle line behind the 

 anterior palatine foramen. 



The septomaxillary is well developed, lying along the greater 

 part of the outer wall of tlie nostril. Most of it is within the 

 nostril, but a small part of the upper end appears on the face. 



The maxilla is not unlike that of Trirachodon. The maxillary 

 branch of nerve v. has two foiamina. On the upper j^art of the 

 maxilla close to the nasal is a small oval depression, presumably 

 for the lodgment of a gland. 



The nasal is narrow in front but broad behind. The nostrils 

 look more upwards than in any of the previously described 

 Cynodonts, and the nasal passes forward between them to a 

 narrow process. 



