THE SKATE. 35 



hinder or occipital region of the skull, and serving for the 

 lodgment of the organ of hearing. 



21. In front of the auditory capsules — the interorbital 

 region — the cranium narrows considerably, but soon widens 

 out again to form 



22. The nasal capsules (Fig. 10, ol), large outwardly 

 projecting masses of cartilage, containing a cavity for the 

 lodgment of the nasal sacs, which cavity is closed above, 

 but widely open below, and communicates with the cranial 

 cavity by a large aperture through which the olfactory nerve 

 (§ 179) passes (see § 32). 



23. In front of the nasal capsules the skull narrows again 

 to form the long projecting rostrum (Fig. 10, r), at the 

 sides of which the two thin rostral cartilages {r.c) are 

 attached. 



24. In the postero-inferior region of the auditory capsule 

 close to where it joins the occipital region, is an aperture 

 leading by a canal excavated in the wall of the auditory 

 capsule, into the cranial cavity, and serving for the transmis- 

 sion of the pneumogastric or vagus nerve (§ 214). 



25. A smaller aperture in the capsule external to the 

 last : this gives exit to the glossopharyngeal nerve (§ 215). 



26. Two considerable apertures in front of the auditory 

 capsule, where it joins the side wall of the skull : the upper 

 and larger of the two is for the transmission of the fifth or 

 trigeminal nerve, the smaller of the two, situated below and 

 ssynewhat behind the first, for the seventh nerve or portio 

 dura (§ 186). 



27. On the upper surface of the auditory capsule, near 

 the fiddle line, is an aperture— that of the aqueductus 

 vestibuli — leading directly into the cavity of the capsule 

 (see § 213). 



28. On the upper surface of the skull, between and in 



D 2 



