52 Proceedings of Royal Society of Edinburgh. [sess. 
(e.) Pharyngeal or Visceral. — This is a branch of the maxillary- 
division of the Vth, and arises ventrally from one of the main 
branches of the maxillary, dipping down and running backwards, 
and ultimately passing on to the pharynx at the point where the 
lower jaw articulates with the skull. It is a slender nerve with a 
long course, and was not traced far on to the pharynx, having by 
this time become extremely fine.* 
The Yth, then, in Ghimcera , is a perfectly typical cranial nerve, 
in so far as it possesses dorsal sensory branches to the skin and 
sense organs, a pharyngeal branch to the mouth, and finally pre- 
and post-branchial branches (maxillary and mandibular). 
Sixth Nerve. — Arises by six rootlets from the ventral pyramids 
of the medulla at a level slightly behind the dorsal root of the 
Vllth. It runs forwards and slightly downwards, and reaching 
the orbit by a foramen under cover of the roots of Vth and Vllth, 
passes straight into the external rectus muscle of the eye, w r hich it 
supplies. 
Seventh Nerve. — This arises from the medulla by three main 
roots, two of which are ventral and the other dorsal. The dorsal 
root (which arises just behind the restiform bodies, and on a level 
with their dorsal border) is connected mostly with the buccal, but 
also with both the other roots by distinct branches. At no point, 
however, is there any confusion between the roots of the Vllth 
and Vth. The seven divisions to be distinguished in the skate 
and Lcemargus exist also in Chimcera. These are : — 
(a.) Superficial Ophthalmic. — Has dorsal and ventral roots, and 
courses over the eye to be distributed to the supra-orbital canal 
(marked by cross-hatching in the figure — SO), and the superficial 
ophthalmic group of ampullae, which with its fellow of the oppo- 
site side occupies by far the greater part of the cavity of the snout. 
As this nerve passes through the canal in the cranium to reach the 
orbit it swells into a large ganglion. 
( b .) Buccal. — Constitutes the main part of the dorsal root of the 
Vllth, and reaches the orbit through a foramen which also gives 
exit to the remainder of the Vllth and the Vth. In passing 
through the cranium it expands into the large buccal ganglion. 
* I might describe other visceral branches of the Yth, but shall postpone 
doing so until I have dissected other specimens. 
