PRIMORDIAL CRANIUM OF THE CAT 299 



canalicularis stands nearly upright in the lateral wall. The 

 external surface of this part rises straight toward the lamina 

 parietalis; the internal surface incUnes from above, ventrad 

 and a little medialward. The cochlear capsule, very large and 

 rounded, lies beneath the brain in the base of the skull, ap- 

 proaching closely its fellow opposite, the two making up almost 

 the entire cranial floor in the otic region. 



At its circumference the otic capsule is connected with neigh- 

 boring parts of the side wall and base of the cranium by broader 

 or narrower stretches of cartilage with intervening vacuities. 

 The several connections between the otic capsule and the occipi- 

 tal wall and basal plate as well as the related openings have 

 already been described (p. 289)'. There remain to be noted the 

 bonds between the capsule and parietal plate, and certain 

 parts in the orbito-temporal region. 



The dorsal, narrow margin of the pars canalicularis is, in 

 large part, free, forming the ventral boundary of the foramen 

 jugulare spurium (figs. 3 and 4). Cephalad and caudad of this 

 narrow fissure it is connected with the lamina parietalis; in the 

 former situation, by the commissura parieto-capsularis, in the 

 latter place with that part of the parietal plate which is con- 

 tinuous ventrally with the occipital wall. Between the cephalic 

 pole of the pars cochlearis and the ala temporalis is the commis- 

 sura alicochlearis which hmits the carotid foramen laterally. 

 Between this opening and the fissura basicochlearis posterior 

 the cochlear capsule is united continuously with the basa. 

 plate (p. 288). 



The pars canalicularis. Outer form 



. Oval and laterally compressed, the massive pars canahcularis 

 stands in the side of the skull, contributing a large part of its 

 lateral wall. It presents an extracranial lateral surface, an- 

 terior and posterior surfaces mainly within the cranium, and a 

 narrow arched dorsal margin. A vestibular region unites this 

 subdivision of the otic capsule with the pars cochlearis. 



The lateral surface (figs. 3, 4) convex and smooth, shows only 

 slight elevations corresponding to the semicircular canals. 



