96 ME. 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. hemitcechus, 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 (PI. 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 i?. megarhinus irom 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 mth 

 the same part in B. bicornis [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. 



Fis. 2. 



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- 



