400 



FOSSILS FEOM PERIM ISLAND. 



the relative proportion of width to lengtli with those of Siva- 

 tlierium. The only other genus of Ruminants which shows 

 the peculiar rugose enamel furrowing, in a marked degree, 

 is the Giraffe, which agrees with the Perim fossil in the simple 

 direction without fold, of the inner crescent of enamel. But, 

 in this genus, the upper premolars are distinguished from 

 those of all other Ruminants by their great excess of width 

 compared with their length. In this respect, and further in 

 being considerably more oblique, both in form and in their 

 relative position in the jaw, these teeth in the Perim fossil 

 differ from those of the Giraffe. The dimensions of the fossil 

 contrasted with those of the Sivatheriun giganteum, and of 

 the skuU of an adult male Giraffe in the collection of the 

 College of Surgeons, are as follow : — 



Length of the three premolars 



Length of the 1st premolar .... 



Width of the 1st 



Length of the 2nd „ .... 



Width of the 2nd 



Length of the 3rd ,, .... 



Width of the 3rd „ .... 



Length of the 1st or antepenultimate true molar 



The second specimen (figs. 3 and 4), (for an examination 

 of which I am indebted to the kindness of Major Jervis, of 

 the Bombay Engineers), is also from Perim Island, and. shows 

 the hindmost premolar, together with the three back or true 

 molars nearly perfect. Like the premolar of the other spe- 

 cimen, these teeth, besides being smaller, differ from their 

 equivalents in Sivatherium giganteum, by the absence of the 

 flexuous direction of the enamel, and of the basal ridge at 

 the inside. In these particulars, and also in the presence of 

 a minute or rudimentary cone of enamel, on the inner side 

 at the base, between the barrel divisions of the teeth, but 

 attached only to the posterior lobe, they correspond with the 

 other molars of the Giraffe. But the anterior pillar of 

 enamel, on the outer surface of the front half of these teeth, 

 is considerably thicker in proportion in the fossil than in the 

 Giraffe ; while the outer surface of the posterior half is more 

 expanded in length, and is more hollow than in the latter 

 genus. A still more important difference is, that in the 

 fossil there is no tendency to a basal mammilla or enamel lobe 

 at the outside between the barrel divisions of the two back- 



