50 PLEISTOCENE MAMMALIA. 



or gracilis and brevis of human anatomy. A comparison of the bone with those of lion, 

 tiger, panther, and jaguar showed no essential point of difference. 



§ 11. Squamosal (Pis. VI, VII, VIII, IX, X, No, 27). — The squamosal consists of a 

 slightly convex scale-like process applied to the exterior of the sides of the cranium, and 

 a stout articular process, which rises at right angles, and forms the pedicle supporting the 

 lower jaw. The former overlaps the ends of the following sutures, commencing ante- 

 riorly, and passing upwards round the edge : — the alisphenoid, parietal, mastoid, 

 petrosal, and tympanic. It is so firmly soldered to the mastoid posteriorly that all trace 

 of the suture is obliterated in the adult. In the young skull, however, of Felis spelaa 

 (PL X, o) it is articulated so loosely that the mastoids have been broken away along the 

 line of weakness thus presented. In the fully grown animal, however, the squamosal, 

 mastoid, petrosal, and tympanic, form one bony mass, which is the exact homologue of 

 the temporal bone of human anatomy. With the parietal it is articulated superiorly by a 

 long horizontal, and with the alisphenoid by a vertical, suture, that ends in the glenoid 

 fissure below. A small part only of the centre of the bone appears in the inner wall of 

 the cranial cavity. Prom the lower and anterior angle of the squamous portion springs the 

 strong pyramidal articular process, triangular in section, with its antero-inferior border 

 deeply excavated, so as to form a transverse horizontal groove, which is the glenoid cavity 

 {p) for the reception of the condyle of the lower jaw. On the postero-inferior surface it 

 is slightly convex, on the superior somewhat concave. At from two to three inches from 

 its origin it suddenly turns forwards at right angles to its long axis, becomes much com- 

 pressed vertically, and is articulated by a long splice or diagonal suture to the malar, by 

 which it is overlapped externally. A strong sigmoid ridge {q), equivalent to the "supra- 

 mastoid ridge" in man, passes forwards from the lower edge of the squamous portion at 

 its juncture with the mastoid, is carried round the upper and posterior edge of the 

 articular process, and forms the upper edge of the zygomatic portion of the bone. 

 Underlying this ridge, at the point where the squamous and articular portions meet, is the 

 meatus auditorius externus [m), or external orifice of the ear, of which the upper edge is 

 formed by the free surface of the bone. At the origin of the ridge, which from its 

 position we may call the squamosal, and abutting against the inferior process of the 

 mastoid, to which it is firmly soldered, is a strong process, in length equal to the latter, 

 that supports the stylo-articular ligament. The depression at its end is marked r in 

 PL VIII. 



Muscles. — The whole space between the zygomatic arch and the cranium is filled by 

 the masses of the great tearing and rending muscle which gives such enormous power to 

 the jaws of the Pelidse and Ilyaenidae — the " crotaphite," or temporal. Its first branch 

 is in part attached to the inner side of the articular process above the malar articulation. 

 The second springs from the squamous portion above the articular process, and the third 

 is partially attached to the general surface of the squamous portion of the base. The 



