552 



APLYSIADiE. 



This family includes a number of Molluscs, some pro- 

 vitled with shells, and some Avanting them, many of which 

 are remarkable for their size and singular aspect. The 

 shell, when present, is internal, and in a manner rudimen- 

 tary. It is contained in a dorsal opercular fold protecting 

 the gills. The head of the animal contrasts with that of 

 the members of the last tribe, in being distinct, and con- 

 stantly furnished with tentacula and eyes. All the species 

 of this tribe are hermaphrodites. 



APLYSIA. LINN.EUS. 



Shell a variously shaped, usually ovate, corneous internal 

 plate, with indications of a rudimentary spire. No oper- 

 culum. 



Animal ovate, convex ; its head pcdicled, furnished with 

 four auriculated tentacula : at the anterior and lateral 

 bases of the upper two are the small sessile eyes. Shell 

 imbedded in an opercular lobe, placed centrally in the 

 back, and protecting the branchial plume, which is not 

 protruded. Mantle with large lateral lobes folding over 

 each other, and protecting the operculum, but capable of 

 being used for swimming. Foot oblong. Mouth subpro- 

 boscidlform, armed with corneous jaws ; tongue armed 

 with a single row of hamated central teeth, and numerous 

 uncinated laterals. Gizzard studded with cartilaginous 



