_ 388 Prof. Owen on Life and Species. 
The discovery of the remains of the Hipparion* supplied — 
one of the links required by Cuvier, between the Paleothe- — 
rium and the Horse of the present day, and it is still more sig- — 
nificant of the fact of filiation of species that the remains of 
such three-toed horses are found only in deposits of that ter- — 
tiary period which intervene between the older paleotherian — 
one and the newer strata in which the modern Horse first ap- 
pears to have lost its lateral hooflets. These relations J illus- 
trated in my Lectures on Fossil Mammalia at the School of 
Mines (1857) by the diagram, fig. 614. 
‘ther evidences of gradation, in the case in question, have — 
been brought to light. The molar series of the Horse includes 
six large complex grinders, individually recognizable by develop- 
mental characters as they are symbolized in fig. 280, p. | 
The representative of the first premolar is minute and soon shed. 
Its homologue in Paleotherium is functionally developed and 
retained, the type-dentition being adhered to.f In Hipparion, 
d, is succeeded by a p,f smaller than in Paleotherium, but func- 
tional, with inflected folds of enamel on the grinding surface, — 
- Paleothere. 
 Hipparion. 
Derivation of Equines. 
* cocmt’’, tom. ii. p. 25 (1832). Another species was discovered in the Miocene 
at Eppelsheim—the *Z erium,’ of Kaup; a third in deposits of similar age 
Sh Se ae a 2 etereeer er re Noman 
— sagt te WD 432. peu plus récents que la molasse dans ces 
| 4, ¥- PL 36, figs. 4 &, 6. coon’, Pl. 19, figs. 1, 1a. 
