2881. ] 487 ieaue. 
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- 
nyz 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 Hetoganus gliriformis. 
CATATHLHZUS RHABDODON, 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 Mioclenus, remind one of TZetraconodon 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. 
ag. Superior premolars enlarged, generally with one external cusp. 
f. A posterior internal cusp of superior molars ; 
Intermediate tubercles present ; last inferior premolar with inner cusp ; 
Catathleus. 
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.........-+0.-eeeeeee everson xe Protogonia. 
ff. No posterier inner cusp of superior molars. 
Intermediate tubercles present; no inner lobe of last inferior premolar 
Mioclanus . 
II. Superior premolars 1, 2 and 3 without inner lobe ; third -with three 
external lobes (Pictet). 
Premolars compressed..... suns aed s abobiieed benks eWailes ses Dichobune. 
In the genus Catathleus 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 cingulum homologous with 
