464 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 27,
points of the hinder horns of each crescent rise into acute eminences,
shows a mode of usure totally different from that which is observed
in R. tichorhinus. Moreover the enamel is far too thin and smooth
for that species, nor does the anterior column exhibit on its inner
face the distinct posterior costa which exists in the lower molars
of R. tichorhinus. I am unable to point out any sufficient character
by which this particular tooth could be distinguished from that of
R. hemitoechus. The size of the tooth is —
Length 2-4 inches. Width 1-15 and 1-2.
No. 881 (Fig. 4) is so much worn as to be of very little use for the purpose of diagnosis. It appears, as stated in the ' Catalogue,' to be pm 4. That it is not tichorhine is obvious enough from the thinness of the enamel. But, except that it is, perhaps, rather more tapering in front, I do not see how it could be distinguished from the same tooth in R. hemitoechus or R. etruscus.
These teeth, therefore, except as regards R. tichorhinus, are of no value for my present purpose. But with respect to the maxillary teeth, the following characters may be adduced as distinguishing them from those of the tichorine Rhinoceros, and, in some measure, from those of any other species.
1. The thinness and smoothness of the enamel.
2. The configuration of the dorsal surface, as seen in —
(a) The lowness of the first and fifth costae — that is to say, of the anterior and posterior angles.
(b) The even undulation of the posterior area, as it is termed by Mr. W. B. Dawkins, and the total absence of the fourth elevation counting from the front, or the fourth costa.
3. The expanded inner end and the pronounced sinuosity on the anterior aspect of the anterior column.
4. The great size of the anterior vallum.
5. The form and connexions of the uncus, and the consequent absence of the true " tichorhine pit."
From the corresponding tooth of Rhinoceros hemitoechus the present seems to differ : —
1. In the lowness of the anterior costa, c 1, and consequent absence of the deep sulcus between it and the second or principal costa.
2. In the comparatively easy undulation of the rest of the dorsal surface.
3. In the thinness of the enamel and, it might be added, of the cementum — a character upon which, however, I think Dr. Falconer was disposed to lay rather undue weight.
4. In the form of the uncus — which, instead of being thick and rounded towards the point, is slender and attenuated, and instead of pointing directly forwards, as in R. hemitoechus, is ultimately directed forwards and outwards *.
- Dr. Falconer, as every one knows, placed great reliance upon the angle
formed between the uncus and posterior column in the discrimination of R.
