114 GASTROPODA. 



FAMILY II. DENTALIAD.E. 



Shell tubular, curved, open at each end, taper- 

 ing ; aperture circular. Animal attached to the 

 shell near the hinder end ; head indistinct, with- 

 out eyes or tentacles ; foot conical, with side-lobes ; 

 gills two, symmetrical ; blood red. 



Dentalium (Linn.). Tusk-shell. [Characters 

 those of the Family.] 



D. entails. Fig. 163; n.s. 

 tarentinum. 



FAMILY III. PATELLAD^E. 



Shell conical, with the summit turned forwards. 

 Animal with a distinct head, eyes, and tentacles ; 

 foot as wide as the shell ; gill-plume one, comb- 

 like ; tongue long, narrow, with numerous teeth. 



Patella (Linn.). Limpet. Shell oval, with the 

 summit more or less central. Animal with the 

 gill-plume very long, surrounding the body, and 

 attached throughout. 



P. vulgata. Fig. 164 ; n.s. 

 pellucida. 

 athletica. 



Acm&a (Esch.). Shell like that of Patella. 

 Animal with the gill-plume lodged in a cavity on 

 the neck, projecting from the right side. 



A. testudinalis. Fig. 165 ; n. s. 

 virginea. 



