1870. ] BUSK—RHINOCEROS OF ORESTON. 465 
5. In the direction of the crista, which, when present in R. he- 
matechus, arises further back from the outer lamina, or even from 
the base of the hinder column itself, and projects in a direction 
nearly parallel with the uncus, instead of at right angles to it. 
2. Other Bones. 
Most of the bones, as I have said, are in a very fragmentary con- 
dition; but amongst them are one or two which are capable of 
affording excellent characters, and are, in fact, alone sufficient, as it 
seems to me, to determine the species to which they belong. 
The first of these is a right middle metacarpal, (no. 905 in the 
Catalogue). The bone is nearly perfect; and its growth is com- 
pleted, inasmuch as no trace remains of the junction between the 
shaft and the epiphysis. 
Regarded with respect either to its size or to its form and pro- 
portions, this bone differs so strikingly at first sight from the cor- 
responding bone in any other species of Rhinoceros, recent or 
extinct, with which I am acquainted, that it is surprising its true 
specific relations should have been so long overlooked. First, as 
regards its size. In Table I. (an which the dimensions and pro-. 
portions of the middle metacarpal, in several instances, of ZR. 
leptorhinus and RR. tichorhinus are given), it will be seen that the 
Oreston bone is nearly 14 inch longer than the longest specimen of 
Rh. tichorhinus of which I have any knowledge, and, in the second 
place, that it nearly corresponds in length with the metacarpal of ft. 
leptorhinus, as shown in two specimens from Grays Thurrock, in 
the British Museum*, As regards the other dimensions, it will also 
be seen considerably to exceed those of R. tichorhinus—as, for in- 
stance, in the size of the two extremities, and especially in the 
transverse diameter of the distal articular surface or trochlea, which 
may be regarded as affording a pretty certain term of comparison. 
With respect to the least circumference of the shaft, it is true that 
in one instance of Lhinoceros tichorhinus that has come under my 
observation, from the river-gravel at Stratford-on-Ayon, the cir- 
hemitechus from R. leptorhinus; and, in the main, I think he was quite right in 
so doing. But it must not, so far as I can judge, be supposed that this cha- 
racter affords an invariable criterion in all cases. Several instances, besides the 
present, showing this, may be cited from the figures given in the ‘ Paleontogra- 
phical Memoirs’ and elsewhere. For instance, in the lower jaw from Lyons, of 
which a figure is given in pl. xxxi. fig. 2, the crochet appears to rise very 
much in the same way as in the Oreston teeth, that is to say, at an acute angle, 
and then to curve outwards. Again, in Mr. B. Dawkins’s fig. 10 (N. Hist. Rev. 
v. p. 410), the crochet cannot be said to arise at an open angle, but the reverse ; 
and the same may be said of the milk-molar, fig. 4 (Zc. p. 405). I have also 
in my possession a mm3 from Ilford, belonging to Mr. Prestwich, in which 
the same may be observed ; and, further, from this specimen it is apparent that 
as the tooth wore down, the angle would become more and more open; so 
that, without throwing any doubt upon the general usefulness of the form of 
the angle as a diagnostic character, it is, I think, one which requires to be used 
with caution. 
* From the close similarity of these two metacarpals from Grays. it is not 
improbable they may be the right and left of the same individual. 
