OSTEOLOG-Y OE THE HYOPOTAMID2E. 
25 
differences from the true Cainotlieria, and the lower molars even more. If we consider 
each lower molar as composed of four parts, two crescents on the outer side and two pillars 
closing the crescents on the inner side (Plate XXXIX. figs. 8-12, ac,pc , ap,pp), then we 
may state that, in the true Cainotlieria from Auvergne, the back part of each posterior 
inner pillar is a little prolonged backwards into a small additional cusp ; this prolonga- 
tion is especially marked on the inner side of the last inferior molar, making the pos- 
terior additional talon of this tooth quite double. This difference may be clearly seen 
in comparing a lower jaw of a Cainotherium from Auvergne with the enlarged figures of 
Pictet (‘ Eaune siderolitique,’ plate xxvi. fig. 9, c). By all these characters the Caino- 
therium Henevieri, Piet., differs from the true Cainotlieria, and agrees entirely with 
the Eocene Ilyopotamidce figured by Butimeyee and by Pictet himself. Therefore the 
Cainotherium Henevieri cannot remain in the genus in which it was put by Pictet, 
but must be arranged with the rest of the Eocene Ilyopotamidce, as Hyopotamus 
Henevieri * . 
I cannot refrain from stating that, in my opinion, the five-lobed character of the upper 
molars is of a too general value to be used for generic distinction. In fact all the 
Eocene and Miocene Paridigitate genera (with crescentic teeth) have five-lobed upper 
molarsf, and therefore this character is as unfit for generic distinction, in this large 
assemblage of animals, as the fact of having four-lobed molars would be found unfit if 
we tried to apply it to the living Euminantia ; it is of too general a nature, all living 
Buminantia having four-lobed upper molars. 
In such cases where the true molars present too great a uniformity for furnishing 
good distinctive characters, the shape of the premolars may be of great use, as was well 
shown by Professors Butimeyer and Hensel, in reference to Suina and Buminantia. 
And, in fact, if we compare the premolars of the Eocene Ilyopotamidce figured by Pictet 
and Humbert, Hyopotamus Gresslyi, II. Henevieri, and even his II. crispus (/. c. plate 
xxiv. fig. 11), we shall see that all these Eocene Ilyopotamidce, though of such different 
size, agree together in the shape of their premolars, while they differ by the same cha- 
racter from the true Miocene Ilyopotamidce from liempstead and Puy. As I hope soon 
to collect materials for a description not only of the dentition but even of the skeleton 
of these Eocene species, I will not enter further into this matter here, and I will only 
state that, by comparing the figures of Pictet with my plates, the reader will perceive 
that the premolars of all the Eocene Ilyopotamidce are, so to say, more ruminant-like: 
this is especially the case with premolars p 2 and p 3 ; they are considerably more elongated 
and not so high as in the Hyopotamus and Antliracotherium. Besides, I suspect from 
some bones seen in the collection in Lausanne, and especially from a metatarsal of 
Hyopotamus ( Cainotherium ) Henevieri figured by Pictet (/. e. plate xxvii. fig. 2), that 
some, if not all, of the Eocene Ilyopotamidce were didactyle, at least the metatarsal 
* The Eocene Cainotherium Court oisi from Yaucluse is identical with C. Henevieri, and therefore must 
share its fate, and he united to the Hyopotamidee. 
f Except Diclwdon and Merycopotamus. 
