272 AMPHIPERASID^. 



lished, callous surfiice the mantle-margin of the animal is 

 probably dilated into lobes covering the sides of the 

 shell ; the transverse elevated ridge is a very peculiar 

 feature in the shell of Cyphoma. 



Species of Cyphoma. 



emarginata, Sow. intermedia, Sow. 



gibbosa, Linn. 



Genus VOLVA, Bolten, 



Mantle-margin with glandular tubercles; foot narrow, 

 longitudinally folded. 



Shell elongately oval, spindle-shaped, ventricose ; aper- 

 ture narrow, with the extremities more or less prolonged 

 into channelled beaks ; columella smooth ; outer lip re- 

 flected, thickened externally. 



Syn. Radius, Montf. Birostra, Swains. Rhizorus, 

 Montf. 



Ex. V. volva, LimKBUS, pi. 29, fig. 1. Shell, V. volva 

 fig. 1, a. 



The foot in this genus is narrow and folded lengthways 

 on itself, being adapted for creeping on the rounded 

 narrow branches of Gorgonim and corals, on which it is 

 supposed to feed ; the animal progresses very slowly, 

 but is tolerably bold in disposition. 



Species of Volva. 



acicularis, Lam. deflexa, Sow. 



acuminata, Sow. formicai'ia, Sow. 



birostris, Lam. frumeutum. Sow. 



coarctata. Sow. gracilis, Sow. 



