442 



OK THE MEMBRAKOUS LABTEINTH OP EHIKA. 



Althougli this replacement by foreign particles is probably 

 peculiar to the genus Bhina, a mixture of otoconia and sand has 

 been found by my friend Mr, E. H. Burne in specimens of 

 Acanthias vulgaris about 2 feet in length, but in ScylUum 

 canicula minute otoconia only were present. It should be noted 

 in this regard that both Acanthias and Hhina are figured as 

 having a similar ductus endolymphaticus of rather large size, 

 that passes through the skin without diminishing and terminates 

 in a large external aperture. In Bhina the apertura externa 

 lies at the anterior border of a spineless, paler, and somewhat 

 sunken patch of skin that in adult fish measured 5 mm. in 

 diameter, those of opposite sides being 11 mm. apart. A saccus 

 endolymphaticus (13 mm. in length) is well-defined from the 

 rest of the duct and lies parallel to the skin. A firm round 

 fibrous baud arises from the skin shortly behind the apertura 

 externa and is attached to the under surface of the saccus 

 throughout its entire length, blending again with the skin 

 immediately in front of it. It is common in Sharks for the 

 cutaneous portion of the duct to be reduced to a tube of great 

 fineness, with only a minute external opening. 



Of course' it is well known that in most Decapod Crustacea 

 sand is introduced into the auditory sac after each moult. 

 Indeed, I have found the shells of Grlobigerinse iu the auditory 

 sac of the Zooea stage of a foreign Crab. 



EXPLANATION OF PLATE 44. 



Fig. 1. Eight membranous labyrinth oi Echinorhinus spinosus. Nat. size. 

 2. Eight membranous labyrinth of Cestracion pMlippi. X 2. 



a. AmpullEB. 

 a.d.e.e. Apertui-a ductus endolym- 

 phatici externa. 

 c.a. Canalis anterior. 

 c.j). Oanalis posterior. 

 c.e. Canalis externus. 

 d.e. Ductus endolymphaticus. 

 d.u.s.p. Ductus utriculo-saccularis 

 posterior. 



f.u.s. Fissura utriculo-saccularis. 

 I. Lagena cochlege. 

 r.n. Eamulus neglectus. 

 rM. Eecessus utriculi. 



s. Saeculus. 

 s.e. Saccus endolymphaticus. 

 ii.a. Utriculus anterior. 

 u.p. Utriculus posterior. 



