136 



SUB-CLASS ELASMOBRANCHII. 



superficial ophthalmic (ramus ophthalmicus super ficialis, sot). 

 This nerve, which is quite inconspicuous in Raji and in forms 

 in which the ophthalmicus profundus is well developed (at once 

 joining the ophthalmic branch of the facial), runs close to or in 

 conjunction with the superficial ophthalmic of the facial ; it 

 is distributed to the subcutaneous tissue and skin of the snout. 

 The main nerve passes on and divides into the superior 

 and inferior maxillary branches. Of these the inferior maxillary 

 is a mixed nerve ; the superior being mainly sensory but con- 

 taining motor fibres in some forms (e.g. Chimaera). 



CSO sot cm 



A' 



FIG. 79. Diagram illustrating the distribution of the dorsal branches of the cranial ne/ves 

 of the lateral line canals, and the position of the groups of ampullae in an Elasmobranch 

 (after Ewart, from Gegenbaur). A auditory nerve with labyrinth ; it also points to the 

 groups of Lorenzini's ampullae ; Bu buccal branch of facial, bu inner branch to part of 

 infraqrbital canal, and to the inner buccal group of ampullae ; bu' its outer branch which 

 supplies the part of the infraorbital canal, and the outer buccal group of ampullae ; 

 ch postbranchial branch of facial to mucous membrane, and giving off motor branches 

 to some jaw muscles ; CSO, CSO supraorbital canal ; CJO, CJO infraorbital canal ; 

 Fa, Fa' roots of facial nerve; Gp glossopharyngeal, arising under cover of the lateralis 

 branch of the vagus nerve ; Hm hyomandibular canal arhing from the infraorbital and 

 giving off the mandibular canal ; the mandibular group of ampullae is in the angle 

 between these two ; Hm' branch of the hyomandibular nerve to the hyoid group of 

 ampullae ; in intestinal branch of vagus with ganglion, where it separates from fourth 

 branchial branch ; In lateralis branch of vagus nerve ; m mouth ; N nasal sac ; om 

 deep branch of oculomotor giving off short root of ciliary ganglion (shown, but not 

 marked), the long root is also shown, as are the short ciliary nerves to the eye ; opr 

 root of ophthalmicus profundus ; opv dorsal branch of same, giving off long ciliary nerves ; 

 pol second branch of lateralis supplying some lateral line sense organs, and a row of pit 

 organs, the first branch supplies the commissure connecting the two lateral canals, and 

 some sense organs of the main canal ; sof ophthalmicus superficial facialis, which 

 supplies the supraorbital canal, and the superficial ophthalmic group of ampullae ; sot 

 ophthalmicus superficialis trigemini ; it arises from the gasserian ganglion ; sp spiracle ; 

 Tr trigeminus ; F 1 , F 2 , F 3 the first three branchial branches of the vagus nerve, each 

 with a ganglion and with pharyngeal, prebranchial and postbranchial branches ; V* the 

 united fourth branchial branch of vagus and intestinal branch; 1-5 gill-slits. 



The facial nerve with its ganglion, the geniculate ganglion, 

 has three or four roots which after communicating with one 

 another separate into three nerves, the ophthalmicus superficialis 



