96 MR. G. BUSK ON THE ANCIENT OR 
In the absence of other direct means of comparison, it is difficult to arrive at any 
positive determination; but, from the circumstance of the Gibraltar atlas fitting so 
exactly as it does upon the skull of R. hemitechus, Falc., it is allowable to assume 
that it must have belonged to a species closely allied to, if not identical with 
that form. 
3. Anterior Extremity. 
One of the best-marked specimens belonging to the anterior extremity is a perfect, 
naturally detached proximal epiphysis of the left humerus (Pl. XI. fig. 1). It includes 
the entire articular surface, the great tuberosity, and the occipital groove and ridges 
complete. The bone is dense and heavy, and is uniformly incrusted on all its surfaces 
with a thin layer of crystalline ferruginous stalagmite. The articular surface measures 
4”-2 in the transverse, and about 5”:0 in the antero-posterior direction. The radius of 
the curve taken tranvsersely is about 2:9, and in the antero-posterior direction about 
2'-0. The occipital groove is three inches wide and about 1-1 deep at the outer side. 
I have not as yet met with the corresponding part of the humerus of any fossil form 
except that of 2. megarhinus from Grays (No. 23111, British Museum), from which the 
Gibraltar specimen differs so widely, more especially in the form of the bicipital groove, 
that there can be no doubt of their specific distinction. I have also compared it with 
the same part in R. dicornis (R. keitloa), with the result that, as regards the form of the 
bicipital groove, it approaches that species more nearly than any other with which a 
comparison has been instituted. In order to illustrate the different and, as it seems to 
me, important characters that are afforded by the conformation of this groove in various 
species of Rhinoceros, I have subjoined ideal sections across it in 
1. The Gibraltar Rhinoceros, fig. 2, 
2. R. megarhinus, Grays, fig. 3, 
3. R. bicornis (R. keitloa), fig. 4, 
in all of which the letter (a) is placed on the outer side. 

Rhinoceros of Gibraltar. 
The specimen No. 7 consists of about the upper half of the left humerus of a 
fully mature, probably aged animal. It is unfortunately much mutilated, the bici- 
