838 On the Extinct Cats of America. [ December, 
Eusmilus, where its proportions are enormous; almost as large as 
in the feline genus S7zi/odon, where they appear to have been an 
inconvenience to the animal. (3) The diminished size of the in- 
ferior canines becomes evident in the lower genera of the third 
division (supra) of the Mimravide, but is most decided in the 
highest genera Hoplophoneus and Eusmilus. (4) The incisor 
teeth have the usual obspatulate or obovate outline in the genera 
of the first and second divisions of the family, including Memravus. 
They are conic in the true sabre-tooths with flared lower jaw, be- 
ginning with Dinictis and ending with Ewsmilus. (5,6 and 7) The 
-structure of the sectorials. The presence of a heel and an inner 
tubercle of the lower sectorial are well known characters of a 
majority of the Carnivora. In only the most highly organized 
genera are they wanting, and among them are included all those 
of the Felide that still exist. In the Mémravide the inferior 
genera have both in a reduced degree, and they soon disappear as 
we ascend the scale. Thus the inner tubercle is only present in 
the species of Proelurus, Dinictis and Hoplophoneus. The heel on 
the other hand remains throughout the entire family. The an- 
terior basal lobe of the superior sectorial has the same history, its 
absence being characteristic of the inferior Carnivora, and of all the 
genera of Nimravide, except in Hoplophoneus, where it is rudi- 
mental. It is well developed in Drepanodon, as in recent Felide, 
and is double in Smilodon neogaeus. (8) The development of the 
inferior flange and lateroanterior angle of the mandibular ramus. 
There is a successive advance in the development of these char- 
acters, beginning with the second group, for in the first they are 
wanting. The lateroanterior angle is developed in Archelurus 
and allied genera, and is merely continued on the inferior border 
of the ramus. In the third group it is much more acute, and 1s 
deflected downwards, forming the well known flange of the sabre- 
tooths. It is longest in the Eusmilus bidentatus Filh. (9) The 
highest genera of Nimravide, e. g. Hoplophoneus, differ from the 
true Felide, in the absence of the cutting lobes on the posterior 
edges of the crowns of the larger premolar teeth. But according 
to Filhol these lobes are present in the generalized genera, yoe- 
lurus and Pseudelurus, which are thus brought into a relation 
with the Fe/ide, not possessed by other Nimravide. 
A characteristic perfection of the Fe/idæe is seen in the genus 
Smilodon; that is, the vertical direction of the ungual phalanges, by 
