. The elasmobranch fishes. Chondrichthyes. 224 THE ELASMOBRANCH FISHES main stems of this complex and out from the cranium through its own fora- men. It enters the base of the external rectus muscle. The facial or seventh cranial nerve like the fifth is composed of four im- portant branches. These are first the superficial ophthalmic nerve {, figs. 200a and 200b) which runs above all the eye muscles through the orbit, gives branches dorsally to the supraorbital sensory canal, and then leaves the orbit by the large anterodorsal ophthalmic foramen (, fig. 47). Out- side of the orbit
. The elasmobranch fishes. Chondrichthyes. 224 THE ELASMOBRANCH FISHES main stems of this complex and out from the cranium through its own fora- men. It enters the base of the external rectus muscle. The facial or seventh cranial nerve like the fifth is composed of four im- portant branches. These are first the superficial ophthalmic nerve {, figs. 200a and 200b) which runs above all the eye muscles through the orbit, gives branches dorsally to the supraorbital sensory canal, and then leaves the orbit by the large anterodorsal ophthalmic foramen (, fig. 47). Out- side of the orbit it supplies branches to the supraorbital canal and to certain groups of the ampullae of Lorenzini. The second or buccal division of the. Fig. 202. Branches of the facial nerve, HeptancMis maculatus. (W. R. Dennes, orig.) , buccalis of facial; , chorda tympani; limd., hyomandibular (postspiracular) division of seventh nerve; , superior and inferior branches of external mandibularis of seventh; , internal division of mandibularis of seventh; , ophthalmicus super- ficialis of seventh nerve; , palatinus; , postspiracular twigs; , prespiracular nerve; sp., spiracle. facial nerve {) passes from the brain stem just dorsal to the maxillary division of the fifth (). In the orbit it divides much like the maxillary division of the fifth. It goes to supply the infraorbital canal and the ophthal- mic and buccal groups of ampullae. The palatine division of the seventh (, fig. 202) leaves the main stem of the hyomandibular nerve and passes ventralward, dividing into an anterior and a posterior branch, to the palate of the mouth. The most posterior division of the facial, the hyomandibular {hmd., figs. 200a and 202), after giving off the palatine branch, passes sharply backward around the spiracle, downward around the angle of the jaw and forward along the mandible. It first gives a prespiracular branch (, fig. 202) to the anterio
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