540 
PEOFESSOE OWEN’S DESCE1PTION OF THE CAVEEN OF 
that complex type ; and these details can only be satisfactorily contrasted, in the absence 
of the specimens themselves, by faithful figures, of the natural size, of the whole dental 
series of the several known species of Equidce. 
Such aid in the determination of the fossil teeth of the Horse-tribe, the want of which 
is greatly felt by palaeontologists, I propose to supply, so far as the materials have been at 
my command ; and I have caused carefully accurate drawings to be made, under my 
inspection, of the grinding- or working-surface of the permanent teeth of the following 
existing kinds of Equines : — 
Equus caballus 6 , E. asinys 6 , E. Burclielli $ , E. zebra (molar series, of nearly adult), 
E. hemionus 6 (or Kiang), and E. quag g a 6 . 
Equus caballus. — The subjects of Plate LVII. figs. 1 & 2, are from a stallion of a 
nearly full-blood hunter, which stood 15^ hands high. 
The series of upper molars have a very moderate degree of curvature, convex outwardly 
(Plate LVII. fig. 1, p 2 to m 3) : the degree of convergence of the right and left series is 
shown in the reduced figure, Plate LXI. fig. 6, Phil. Trans. 1869, Part II. The first 
functional premolar (Plate LVII. fig. 1, p 2) has the grinding-surface anteriorly produced 
and pointed, a! ; the last grinder, to 3, has the same surface contracted posteriorly, but 
less produced and ending more obtusely ; its antero-posterior extent exceeds that of the 
contiguous molar, to 2, in a greater degree than in smaller varieties of Eq. caballus (see 
Table of Admeasurements, p. 552). In all the molars the outer longitudinal channels, 
f,f, are broad and more or less flat at the bottom, the anterior on e,f, being the deepest, 
the posterior one, f\ having the posterior boundary least defined ; and that boundary is 
wanting in to 3. The intervening ridge, n, is rather broad, is flattened, and in the pre- 
molars is slightly indented or canaliculate. The lobes, a, b, are irregularly crescentic, 
with a slightly wavy enamel contour. The internal lobe, to, is oblong, antero-posteriorly 
produced both backward and forward, as at p ; but, in this direction, least so in p 2, 
most so in to 3. It is represented by the circular summit of a detached column of ena- 
melled dentine in Hipp avion (cut, fig. 3, to). The hind end of to 3 is subbilobed. The 
length of the upper molar series is 7 inches 6 lines ; the premolars forming rather more 
than half that extent. 
The right and left series of upper grinders very slightly converge anteriorly. The 
interspace between the hindmost grinders is 3 inches 2 lines ; that between the foremost 
is 2 inches 4 lines. 
The series of the lower grinders (Plate LVII. fig. 2) is straight, equally divided between 
the false and true molars ; the whole, as in other Ungulates, are narrower in proportion 
to their fore-and-aft breadth than the upper grinders, upon which they work as does 
the hammer upon the anvil ; and they decrease in transverse thickness from the penulti- 
mate premolar (p 3) backward. 
The outer longitudinal groove, i, indents the crown more deeply as the grinder recedes 
in position, at least from p 2 to to 2. The antinternal enamel-fold, Jc, bifurcates more 
completely than in Hipparion , the anterior prong being short and inclining outward ; 
