300 ROBERT J. TERRY 



Rounded prominences at the cephalic and caudal poles, which 

 appear on both the medial and lateral aspects of the otic capsule, 

 are identified as the prominentia utriculo-ampullaris superior 

 and the prominentia utriculo-ampullaris inferior, respectively 

 (fig. 10). The lateral surface of the pars canalicularis terminates 

 ventrally in a broad irregular ridge, the crista parotica, which, 

 projecting basally, extends from the superior utricular promi- 

 nence the full length of this surface. In its caudal half the 

 crista parotica (figs. 2, 20) gives rise to an oval elevation con- 

 nected medially with the base of Reichert's cartilage. The ele- 

 vation bears a close relation to the future processus mastoideus, 

 which in the cat belongs exclusively to the otic region; but that 

 it gives rise to it I am unable 'to say. The parotic crest, es- 

 pecially in its caudal two thirds, projects from that part of the 

 ear capsule lodging the lateral semicircular canal. In its cephalic 

 part is a slight depression of its lateral surface, the fossa incudis 

 (fig. 3) where the cartilaginous incus is connected by a Uga- 

 ment. A tegmen tympani at the stage represented by the 

 model is not present. Further relations of the crista parotica 

 with Reichert's cartilage, and the facial canal will be discussed 

 under these subjects. A deep groove separates the crista parot- 

 ica from the pars cochlearis. This can be traced anteriorly 

 beyond the limits of the crest upon the inferior cochlear promi- 

 nence toward the foramen faciale; posteriorly as far as the 

 jugular foramen. The facial foramen (fig. 1) transmitting the 

 N. facialis, is directed antero-laterally and lies without the plane 

 of the membrana limitans (vide infra). Here is formed the 

 geniculate ganglion and the origin of the great superficial petrosal 

 nerve. In its anterior part the groove lodges the facial nerve 

 and is identified as the sulcus faciaUs. At the base of Reichert's 

 cartilage it becomes narrow through the approximation of this 

 cartilage toward the crista parotica and the wall of the coch- 

 lea, here forming the promontory (fig. 12). Since, at this spot 

 the nerve makes its exit from the groove, it is to be regarded as 

 the foramen stylomastoideum primiti\Tim. Caudad of this 

 foramen, the gToove is broad and deep, filled with connective 

 tissue and occupied to a small extent by the hinder part of the 



