1850.] 91 



It has been frequently remarked in works on anatomy, that in man, the squa- 

 mous portion of the temporal bone enters into the construction of the cavity of 

 the cranium comparatively more than in any other animal, but in the fossil before 

 us we find it to be comparatively much greater than in man, for although the 

 cranium is but little larger than that of the beaver, yet the squamous portion of 

 the temporal bone in it measures over two inches in breadth antero-posteriorly, 

 and one and three-fourths of an inch at its highest point. The summits of this 

 portion of the two bones are not more than seven-tenths of an inch apart at the 

 top of the head. The exterior surface of the squamous bone is very slightly con- 

 vex, nearly flat, and inclines at an angle of about 50. It is bounded postero- 

 inferiorly by a strong, projecting ridge, the superior root of the zygoma, which 

 commences almost vertically above and a very little behind the meatus audito- 

 rius externus. The origin or commencement of this ridge indicates considerable 

 advancement of the squamous bone. Just within the ridge posteriorly on a line 

 with the meatus auditorius externus, is a large round venous foramen, the direc- 

 tion of which is downwards and inwards. 



The base of the zygoma is remarkably strong, its direction being at first almost 

 directly outward. The glenoid cavity is of unusually large extent, even greater 

 than that of most known Ruminantia, and is placed immediately beneath tne 

 base of support of the zygoma, more like in man and the quadrumana than in other 

 animals. In its direction it is transverse, with an inclination from within outward 

 and a little upward. Posteriorly it is bounded by a comparatively enormous 

 tuberosity separating it from the meatus auditorius externus, which at its longest 

 part internally measures 7-lOths of an inch from the floor of the meatus, 

 i an inch in thickness at the base, antero-posteriorly, on a level with the 

 bottom of the glenoid cavity, and over 6-lOths of aninchtransversly. Anteriorly 

 the glenoid cavity is bounded by a broad transverse ridge, about two lines higher, 

 anterior to which is a large inferior concave surface extending inward and for- 

 ward to the root of the pterygoid processes and the spheno-orbitar foramen, 

 bounded on the exterior of the latter by a projecting ridge of the alisphenoid. 

 Posterior to the posterior glenoid tuberosity, and the superior root of the zygoma, 

 is a nearly vertical triangular excavation, bounded posteriorly by the mastoid 

 and para-mastoid processes, and containing the meatus auditorius externus bounded 

 below by a strong, semicircular auditory process. In a groove between the latter 

 and the post-glenoid tuberosity, is placed a second small tuberosity or ridge about 

 1 line in length. Continuous with the groove just mentioned around the base 

 of the posterior glenoid tuberosity internally, is a deep fissure, having at its bottom 

 two glenoidal foramina. Bounding the fissure on the inside, is a large, compressed 

 globular auditory bulla, measuring about 7-lOths of an inch vertically, and 

 antero-posteriorly, and 6-lOths of an inch transversely. Posteriorly it abuts 

 against the para-mastoid process, and antero-externally it joins the alisphenoid by 

 a prominent ridge just within the suture, separating the alisphenoid from the 

 squamous bone. Poslero-externally, bounded posteriorly by the para-mastoid, 

 and externally by the auditory process, is a deep vertical pit at the bottom of 

 which is a round basis of support for the styloid process of the temporal bone. 

 Antero-internally to the auditory bulla, between it and the basisphenoid and 

 alisphenoid, is a large oval pit, the foramen lacerum anterius, and the caroticum 

 combined. Anterior to this, placed in the alisphenoid between the auditory 



