THE ELASMOBRANCII FISHES 



279 



poral canal is supplied by a few twigs of the supratemporalis IX (Chlamydo- 

 selaehus, Laemargus, Squalus acanthias, fig. 245, st.IX) and the most anterior 

 part of this segment is supplied by a few fibers from the ramus oticus VII. 



The supraorbital canal is supplied by branches from the ophthalmicus 

 superficiaJis of the facial nerve, and the infraorbital by the buccalis nerve, 

 while the nenromasts of the hj-omandibular and mandibular canals are sup- 

 plied by the external mandibular division of the seventh nerve. 



FUNCTION OF SENSORY CANAL SYSTEM 



The function of tlie sensory canal system has l)een made the subject of many 

 studies. It was observed by early workers that the pores contained mucus. The 



Fig. 245. Innervation of the Sensory canal system and certain of the pit organs, Squalus 

 acanthias. (From Norris and Hughes.) 



bu.FII, buccalis nerve; cc, suprateniporal canal; dr.X, ramus dorsalis of tenth nerve; 

 liinc, hyomandibular canal; ioc, infraorbital canal; U., lateral line canal; Jl.X, lateral line 

 nerve; mc, mandibular canal; mde.VII, external mandibular nerve; os.FII, ophthalmicus 

 superficialis of seventh nerve; po., pit organs; soc, supraorbital canal; st.IX, supratem- 

 poralis of ninth nerve ; st.X, supratemporalis of tenth nerve. 



system was therefore taken to function in the production and distribution of 

 mucus and the pores were therefore called mucous pores. Later study also 

 demonstrated the relation of these organs to the nervous system. 



It has been shown by G. H. Parker (1904) that a shark which has been de- 

 prived of hearing and sight responds to wave movement, like that produced by 

 throwing a stone into the water, so long as the nerves to the lateral line are 

 intact. When these nerves are cut, however, no further response is given. 



Ampullary Organs 



The ampullary sense organs, as in Heptanchus, are confined to the head and 

 are generally arranged in four or five groups. These are, in Squalus sucMii 

 (fig. 241), the supraophthalmic (soa.), the inner (iha.) and outer buccal 

 (oha.) groups; and the mandibular just behind the mandible; and the hyoid 



