A treatise on zoology . ranch; continuing asa short temporal canal and a postorbital canal, it divides into adorsal supraorbital and a ventral suborbital branch extending onto the snout. Portions of a hyomandibular and mandibular canalare also present, though generally interrupted (cp. p. 220, and Figs. 126 EL A SMOBRANCHII 85 and 196, where the nerve-supply of these canals is given). Thevery characteristic groups of sensory ampullae, supplied by thefacial nerve (Fig. 84), are distributed on the head, as shown inFigs. 11 and 85. These deep-seated organs communicate with theexterior by long tub
A treatise on zoology . ranch; continuing asa short temporal canal and a postorbital canal, it divides into adorsal supraorbital and a ventral suborbital branch extending onto the snout. Portions of a hyomandibular and mandibular canalare also present, though generally interrupted (cp. p. 220, and Figs. 126 EL A SMOBRANCHII 85 and 196, where the nerve-supply of these canals is given). Thevery characteristic groups of sensory ampullae, supplied by thefacial nerve (Fig. 84), are distributed on the head, as shown inFigs. 11 and 85. These deep-seated organs communicate with theexterior by long tubes opening by conspicuous pores on the surface(Fig. 84). Among the characteristic features of the brain one may mentionthe following. The prosencephalon (Fig. 7) is large, of jaairedorigin, and may contain paired cavities, but shows little or no signof external division, especially in the Rajiformes. The thickenedfloor and wall of the telencephalon merges in front Avith that of the scf. soa. pr. so hr ^^- ^^? stv. (ha. mx Diagram of the head of Laemargus, showing the cranial nerves and sense-organs. ( Mitcheli.) The lateral-line canals are indicated as in Fig. 196, p. 222. a, auditory labjTinth;ad, auditory nerve ; b, buccal branch of facial; c, ciliary ganglion on branch of oculomotor;e eye ? n, epibranchial ganglion on branch of vagus ; gl, glossopharyngeal; , hyoid groupof ampullae of Lorenzini ; ^»i, hvomandibular branch of facial ; , inferior group of ampullae;, intestinal branch of vagus ; , lateral-line canal of trunk ; , lateral-line branch of vagus ;m ( mandibular gioun of ampullae ; mx, jnaxillary branch of trigeminal; , nasal sac ; ,suborbital group of ampullae ; , pit-organ ; pr, profundus ; , post-trematic branch ofbranchial nerve ; , superior ophthalmic branch of trigeminus ; , superior group ofampullae ; , superior ophthalmic branch of facial; sp, spiracle ; , supratemporal branchof vagus ; ,
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