the Skull of DiaJcmodon. 329 



D. entomophonus is distinguished from D. broivni by : — 

 1st. Tlic rather larger inner lobe of the penultimate molar. 

 !L*nd. The third molar is nearly as wide as the fourth, 

 being j ; of it. 



D. mastacus is easily distinguished : — 



1st. By the very large size of the inner lobe of the 

 penultimate tooth. 



2nd. The third tooth is if, of the flidth of the fourth, 

 but is very long antero-posteriorly. 



D. jiolyphayus most unfortunately does not show the 

 characters of the last three molar teeth. It is distinguished 

 from all the species recorded above by the fact that the 

 fourth tooth from the back is extremely short, much shorter 

 tbau the fifth. 



In this species the posterior borders of the secondary 

 plates of the palatines meet in au almost straight line, a 

 condition markedly ditferent from that in D. browni. (This 

 diiierence is exactly parallel to that which separates the 

 crocodilian genus Steneosaurus I'rom the more primitive 

 Mystriosaunis.) 



The other skull figured by Sceley as Gomphoynathus 

 poiyphayus has the lower jaw closed on the palate, so that 

 the characters of the dentition are not visible. The last 

 molar as seen in side view has the same baekwardly curved 

 crown of the last upper molar as Diademodon browni. This 

 skull in the character of the back of the palatines agrees 

 with D. polyphayiis. It differs from the type of this species, 

 however, in being proportionately broader over the squa- 

 mosals and in the much greater distance between the 

 foramina jugularcs. 



It will probably be best for the present to leave it without 

 specific determination. 



D. kannemeyeri, the type of Goinphoynathus, differs from 

 D. broivni and D. sp. in the much shorter diastema in the 

 mandible. As the upper 'teeth are unknown it cannot be 

 further defined. 



D. dimorphodon differs from all the above species in which 

 the lower jaw is known, in the fact that the hinder part of 

 the long diastema shows the roots and worn-down crown of 

 anterior cheek-teeth. 



In conclusion, I wish to express my great indebtedness to 

 Drs. A, S. Woodward and C. W. Andrews, of the British 



