536 Prof. J. C. Ewart. 



corresponding nerves in Lcemargus, and, as in Lc&margus, they never 

 present ganglia in any part of their course. 



There is the usual ganglion on the trigeminal nerve, and this nerve 

 (3, fig. 2), as in Lcemargus, divides into maxillary (3', fig. 2) and 

 mandibular (3", fig. 2) branches, and sends a superficial ophthalmic 

 branch to the snout along with the ophthalmicus superficialis of the 

 facial. The facial complex, again, consists of four nerves, viz.: (1) 

 the ophthalmicus superficialis (4, fig. 2), with a large ganglion, which 

 lies immediately above and in front of the Grasserian ganglion ; (2) 

 the buccal (5, fig. 2), with a ganglion lying over the origin of the 

 mandibular branch of the trigeminal ; (3) the palatine (6, fig. 2), 

 (with an indistinct root containing gaiigl ionic cells) which gives off 

 palatine and prespiracular branches, and a branch which extends 

 outwards to unite with fibres from the hyomandibular and bend 

 round the hyomandibular cartilage, and eventually reach the floor of 

 the mouth behind the mandible, thus resembling the chorda tympani ; 

 and (4) the hyomandibular nerve (7, fig. 2), which is chiefly distri- 

 buted to mucous canals and the ampullae of sensory tubes. To the 

 hyomandibular a large bundle of fibres is contributed, as in Lcemargus, 

 from the upper border of the ophthalmicus superficialis. 



The auditory nerve (10, fig. 2) lies in contact with the hyoman- 

 dibular, and has numerous ganglionic cells in its root. 



The glossopharyngeal nerve (11, fig. 2) runs forwards from under 

 the root of the lateralis nerve, and, bending backwards, passes out- 

 wards through a canal which opens into the floor of the cavity of the 

 auditory capsule. Passing through the cavity of the capsule, the 

 nerve next penetrates its outer wall, and at once expands to form a 

 large oval ganglion, from which the usual branches take their origin. 

 A dorsal branch, which reaches the surface of the head, does not seem 

 to supply any portion of the occipital or aural mucous canals. 



The vagus complex (12, fig. 2) in some respects seems to be more 

 primitive in the skate than in any other Elasmobranch. It may be 

 said to consist of six nerves, all of which can be readily distinguished, 

 and each nerve presents a distinct ganglion. These nerves are (1) the 

 lateralis (Z, fig. 2), which springs by a special root above and in front 

 of the glossopharyngeal nerve. The ganglion of the lateralis varies 

 in position, being sometimes situated nearly two inches beyond the 

 point at which the nerve issues from the cranium, in other cases 

 only half an inch from its point of exit. A slender branch arising in 

 the vagus canal arches upwards to supply the anterior portion of the 

 canal of the lateral line, the aural, and part of the occipital mucous 

 canals. The main trunk of the lateralis is distributed to the rest of 

 the canal of the lateral line and to the posterior pleural canal. 

 (2.) The four branchial nerves. The first three branchial nerves 

 (2 4 6, fig. 2) acquire an independent existence almost as soon as the 



