54 PLEISTOCENE MAMMALIA. 



gular plates, convex vertically and horizontally, and thin except at the point of junction, 

 where they form the strong sagittal crest for the attachment of the third branch of the 

 temporal muscle. This crest increases in size and height, as in the recent Eelidse, in pro- 

 portion to the age, being almost obsolete in the young animal that has not yet had time to 

 use his jaws for tearing and rending, and gradually increasing in size in proportion to the 

 age, and consequently the increased use of the temporal muscle, until it reaches its maximum 

 in the old tiger. From the lower anterior angle of the bone a process is sent downwards 

 and forwards to meet the alisphenoid, on which frequently in old lions, and in the smaller 

 spelaean skull in Taunton, there is frequently a strong ridge defining the points of attach- 

 ment of the second and third branches of the temporal muscle. The size and situation of 

 this ridge recall the vast parietal processes in the genus Otaria, in which also the ramal 

 process of the lower jaw, described by us as characteristic of lion and Felis spelaa, is 

 enormously developed. Anteriorly they overlap the frontals by a straight suture ; pos- 

 teriorly they are overlapped by the Wormian ; but in old age the latter suture is 

 obliterated ; it is very variable in position in the larger Feles, generally running clear of, 

 and in front of, the occipital crest, but sometimes occurring in the crest itself. In- 

 feriorly they are to a great extent covered by the squamosals, which almost entirely 

 conceal their alisphenoidal processes, and entirely their long posterior processes, which 

 may be called " petrosal," from their close contact with those bones. 



Internal surface. — A plate, thin in the smaller but very thick and strong in the larger 

 Feles, projects downwards from the cranial surface of the parietals, running diagonally 

 forwards from the posterior angle of the symphysis to the petrosal process, where it is 

 united to a small corresponding plate on the alisphenoid. This plate, Avith its fellow of 

 the opposite side, forms the " tentorium " (PL X), or ossified^ curtain of the " dura 

 mater," that divides the cerebrum from the cerebellum. In the centre of the united 

 processes is an arch rather more than half the height, and about one third of the width of 

 the cranial cavity, which admits of the connection of the cerebrum and cerebellum. The 

 symphysis between them projects forwards into a ridge, which is high and sharp in the 

 larger Felidae, and which sends down a sharp spine, which may be called the tentorial. 

 This latter is present in tiger, but altogether wanting in lion and Felis sjjelaa. In the 

 former, also, the arch appears to be narrower than in the two latter. 



The whole of the cranial surface of the parietal and tentorium is ridged and furrowed 

 for the convolutions of the brain. 



Nearly the whole of the ten)poral surface of the bone is occupied by the great third 

 branch of the temporal muscle, which has its principal attachments along the posterior part 

 of the sagittal crest. The other muscles associated with the sagittal crest are small, and 

 spring rather from the Wormian, and the front of the occipital crest rather than from the 

 parietal. They are all connected with the movement of the ear, and are termed by 



' PI. X, "tentorium." 



