1881.] 487 [Cope. 



posed than the internal, and are somewhat contracted inwards. In the 

 unworn crown there is a distinct anterior inner cusp, which is soon con- 

 founded on attrition. The heel of the last premolar has a crescentic sec- 

 tion, the internal horn the narrower. The anterior lobe is a robust cone. 

 The base of the second and third premolar is oblique to the axis of the 

 ramus outwards and forwards. It is possible that there is a minute first 

 premolar filling the short space between the second and the canine. 

 No cingula ; enamel obscurely plicate, ramus robust. Length of molars 

 minus the last .0465 ; length of base of first true molar .010 ; width of do. 

 .009 ; elevation of crown do. .0055 ; length of base of fourth premolar 

 .011 ; width of do. .008 ; elevation of crown of do. .0065. Anteroposte- 

 rior diameter of base of crown of canine .010. Depth of ramus at first 

 true molar .023 ; width of do. at do. .013. This genus differs from Estho- 

 nyx in the form of the fourth premolar. In the latter the anterior lobe is 

 compressed and trenchant. The species is larger than any of that genus, 

 and nearly equal to the Ectoganus gliriformis. 



Catathl^us ehabdodon, gen. et sp. nov. Char. Gen. With this 

 genus I commence descriptions of several genera with bunodont denti- 

 tion, which has some resemblance to that of some of the hogs. The one 

 above named, with Mioclcmus, remind one of Tetraconodon Falc. and 

 Lydd., in the enlarged proportions of their premolar teeth. . I compare the 

 genera as follows, introducing a probably perissodactyle form {Protogonia) 

 for comparison : 



I. Third and fourth superior premolars one or two lobed externally, and 

 with internal lobes. 



a. Superior premolars with two external lobes ; inferior fourth with 

 two median cusps. 



Intermediate tubercles ; premolars not enlarged Phenacodus. 



o.o.. Superior premolars enlarged, generally with one external cusp. 

 /5. A posterior internal cusp of superior molars ; 

 Intermediate tubercles present ; last inferior premolar with inner cusp ; 



Catatlilcms. 

 Intermediate tubercles wanting, replaced by branches of an internal V ; 



no cusp on inner side of last inferior premolar Anisonchus. 



Intermediate tubercle present, connected with anterior inner by ridges ; 



inferior molars with Vs Protogonia. 



j3j3. No posterier inner cusp of superior molars. 

 Intermediate tubercles present ; no inner lobe of last inferior premolar 



Miodcenus . 



II. Superior premolars 1, 2 and 3 without inner lobe ; third with three 

 external lobes (Pictet). 



Premolars compressed Dichobune. 



In the genus Gatathlceus the development of the premolars is remarkable 

 while the true molars are relatively small. The last three superior pre- 

 molars have an elevated internal crescentic cinsulum homologous with 



