56 PLEISTOCENE MAMMALIA. 



temporal surface is united to the temporal process of the aUsphenoid by a small process 

 passing into the anterior and upper angle of that bone. Thence it passes obliquely back- 

 wards to join the straight, transverse, parieto-frontal suture, that has akeady been 

 described. 



The boundary between the frontal and orbital surfaces is the " superciliary" ridge, 

 that between the frontal and temporal the " temporal ;" and these two unite in the 

 massive supra-orbital process (/). The frontal surface is generally wider and flatter in 

 the fully adult lion than in the tiger ; and in the latter animal it rises on either side of the 

 inter-frontal suture into a well-defined rounded elevation, so that the entire mass of the 

 supra-orbital process is directed more decidedly downwards than in the former animal. 

 In lion the surface is more or less widely concave, and the mass of the supra-orbital 

 process is nearly horizontal, the point only being directed downwards. Some aged 

 skulls of lion, however, and particularly in the smaller varieties, approach those of 

 the tiger in this respect ; and the young of each species are, as one might expect, to be 

 determined only with great difficulty as far as this character is concerned. But as we 

 can discriminate adult leonine skulls from those of tiger in every case that has come 

 before us by this character alone, we believe that it is tolerably constant. The smaller 

 spelaean skull (PI. IX) agrees with the average and therefore typical lion in the possession 

 of this characteristic, as also does the larger specimen (PI. X), so far as its abraded 

 condition allows us to judge. The small skull in the British Museum, from Sundwig, 

 on the other hand, is somewhat tigrine in this respect, but not more so than small 

 skulls of Felis leo in the same collection. Across the inter-frontal suture, at a small 

 distance from the nasal notch, a semilunar depression^ exists in many skulls of tiger, 

 that is only slightly indicated in those of lion. We do not, however, find this constant. 

 In all the three spelaean skulls this depression is absent. 



The temporal ridges bounding the posterior part of the frontal surface pass diagonally 

 backwards from the supra-orbital process on either side to unite in the sagittal crest. In 

 the young of the larger and in the adult of the smaller Feles, they pass far over the 

 parietal before they join, so that the sagittal crest does not reach as far forwards as the 

 frontal bone. In the adult tiger it passes over the parieto-frontal suture, sometimes to 

 the extent of an inch and a half before its point of junction with the ridges, while in the 

 adult lion its extent on the frontal bone is very small, and in many cases the temporal 

 ridges extend as far back as the parieto-frontal suture. In this respect the smaller skull 

 of Fells spelaa (PI. IX), which is that of an old animal, is typically leonine, and the larger, 

 though younger, figured in (PI. X), shows the same tendency, as does also, though in a 

 somewhat less degree, that from Sundwig. Also, if a line be drawn across the frontal 

 surface joining the posterior edges of the supra-orbital processes, and from the pohit 

 where it cuts the inter-frontal suture a measurement be taken to the fronto-parietal 



' See Owen, ' Proceed. Zool. Soc.,' Jan., 1834, p. 1. 



