GASTEROPODA. 



147 



side perforated with small holes. Animal, shaped like the 

 shell, its head terminating in a short muzzle, and bearing- 

 two subulate tentacles and two stout eye peduncles at 

 their external bases ; a fimbriated lobe between the ten- 

 tacula, apparently continuous with the fimbriated and cir- 

 rhated lateral lobes of the body ; lateral cirrhi numerous ; 

 foot very large, oblong, rounded at the extremities, bear- 

 ing on its upper extremity a rudimentary operculigerous 

 lobe, but no operculum; branchial plumes two; dental 

 system consisting of a median tooth flanked by two laterals, 

 four primary accessorials and numerous secondaries.* — 

 73 species f; also fossil. 



The form of this shell somewhat resembles that of the 

 human ear, and it is from that circumstance frequently 

 called the Ear-shell; one species, from its length, having 

 received the name of the Ass's Ear. The outside is gene- 

 rally rough, worn or covered with marine substances ; the 

 inside presents the same enamelled appearance as mother- 

 of-pearl, and exhibits the most beautiful colours. The 

 holes with which the shell is perforated are for the passage 

 of the lobes of the animal's mantle, and are made at regular 

 intervals, as it increases in size. It is observable, how- 

 ever, that as each new one is formed the one nearest the 

 spire is closed up ; so that there are generally the same 

 number open at a time, and seldom more than seven or 

 eight. The annexed cut is a representation of one of the 

 species of this curious genus, with its living inhabitant, 

 which, notwithstanding its apparent size, can be covered 

 by the shell. In its state of rest, it is able to adhere with 

 such tenacity to the substance it is fixed upon as to be 

 removed with very great difficulty, although it can detach 

 itself with ease. It is always found near the surface of 



* Forbes's British Moll. 



f Reeve's Iconics. 



