FKOM THE SIYALIK HILLS. 129 



cusp is present. The cmgulum is very pronounced, except pos- 

 teriorly, and swells antero-internally into a talon-like prominence, 

 from which a well-defined ridge ascends up the crown. The third 

 premolar differs from the preceding in its greater size and in having 

 the posterior accessory cusp proportionately less developed. The 

 fourth premolar or sectorial consists, as usual, of a blade divided into 

 three lobes and of a stout trihedral internal tubercle, separated from 

 the outer lobes by a deep valley ; the elongation of the posterior 

 lobe of the blade approximates the fossil to H. croaita. But the 

 tubercular is still more highly developed proportionately than in the 

 living Indian Hyaena, thus differing remarkably from the Cape 

 Hyaena. This tooth is triangular and three-fanged. In the lower 

 jaw, the fijst and second false molars (pm. 2 and pm. 3) are entirely 

 devoid of the anterior accessory cusps so well developed in H. stHata, 

 The third premolar (pm. 4) consists of a principal cone, a rudimen- 

 tary anterior accessory cusp, and a tolerably well-developed posterior 

 one. Two prominent longitudinal ridges, one anterior and the 

 other posterior, ascend up the principal cone and divide it into two 

 faces, of which the outer is much more convex than the inner. 

 The dimensions of the tubercular part of the first molar or carnas- 

 sial are intermediate between those of the corresponding part in the 

 striped and the Cape Hyaenas. The accessory cusp at the inner and 

 posterior part of the base of that tooth is either entirely absent or, 

 if present, quite rudimentarj% thus differing remarkably from the 

 living Hyaena of India, and approximating to Hycena crocuta. 



The large tubercular molar of the upper jaw in the fossil under 

 examination differentiates it from H. sjpelcea and the allied species, 

 or, rather, varieties, H. intermedia and H. Perrieri*, It is distin- 

 guished from H. ]prisca and H. arvernensis by the absence of the 

 anterior accessory cusps in the premolars t. The antero-posterior 

 length of the upper tubercular in R. Jiip'parionumX is proportion- 

 ately much greater. H. eximia § is separated, by the presence of 

 premolar 1 in the lower jaw, from all other known species of 

 Hyaena. 



In its general outline the skuU resembles that of H. striata. As 

 in the latter, the brain-case is swollen behind and not laterally com- 

 pressed as in H. crocuta or its allied fossil H, spelcea. The sagittal 

 crest is very well marked. The lambdoidal crest is not so much re- 

 flected back at its apex as in H. sj)el€ea. The postglenoidal pro- 

 cesses are very stout and strong. The postorbital processes of the 

 frontal are very well developed, and are proportionately longer than 

 in any other known species. 



It will be seen from what has been said that while in certain 

 characters, as in the form of the skull, the dimensions of the upper 

 tubercular, &c., jET. sivalensis comes near to the most primitive of the 

 three living species of Hyaena, in certain other characters, and 



* W. Boyd Dawkins, 'Nat. Hist. Rev.' 1865. 



t BlainvHle, 'Atl. d'Ost.' gen. Hymna, pi, viii. 



X Gervais, ' Zool. et Pal. Fr.' p. 242, pi. lii. 



§ Gaudry, ' Anim. foss. et Geol, de rAttique,' p. 82, pis. xii., xiii., xir. 



.J.G.S. No. 141. K 



