270 



THE ELASMOBRANCH FISHES 



will be observed that in a type like Acanthias (fig. 233a) the lens is suspended 

 by a dorsal suspensory ligament (si.) and is joined ventrally and laterally by 

 a muscle (l.m.) from the iris. This might be regulatory in that it would draw 

 the lens slightly forward but the lens cannot be focused with precision as it 

 can in man and other higher animals. 



C D 



Fig. 236. Ear of Elasmobranchs. (Olive Swezy, orig.) 



Squalus sucldii: A. Outer view of left ear. B. Inner view of right ear. 



Heterodontus francisci: C. Outer view of left ear. D. Inner view of right ear. 



a.a., ampulla of anterior oblique semicircular canal; a.h., ampulla of horizontal canal; 



aos., anterior oblique semicircular canal; a.p., ampulla of posterior canal; d.c, connection 



from posterior canal to sacculus; e.d., endolymphatic duct; e.s., endolymphatic sac; 



/ir., horizontal canal; /., lagena; pos., posterior oblique semicircular canal; ra.a., ramus 



of eighth nerve to ampulla of anterior oblique canal; ra.h., ramus to horizontal ampulla; 



ra.n., ramus to macula neglecta ; ra.p., ramus to posterior ampulla ; ra.s., ramus to sacculus; 



ra.u., ramus to utriculus; r.u., recessus utriculi; s., sacculus; ii., utrieulus. 



