828 



The latter genus and Stomatia possess the faculty, common to 

 some other kinds of Mollusca, of spontaneously detaching a con- 

 siderable portion of tlie hind part of the foot, when disturbed or 

 irritated. 



Very possibly the genus Anatomus of Montfort, or the Scissu- 

 rella of D^Orbigny, although the operculum is said to be present, 

 may likewise belong to this sub-family of Trochida. 



Genus GENA, Gray. 



Animal subspiral, oval, depressed, too large to retract entirely 

 within the shell; frontal lobes plumose; foot very large, thick, 

 fleshy, tubercular, posteriorly greatly produced, lateral membrane 

 not fimbriated, more or less extended, and covering the sides of 

 the shell. 



Operculum none. 



Shell subspiral, oblong, ear-shaped, depressed, smooth or stri- 

 ated; spire flattened, nearly obsolete; aperture large, pearly 

 within. 



1. Gena lutea (pi. clxxiii. f. 4, 5), Linimus (Patella), Syst. 

 Nat. ed. 10. p. 783. Stomatella auricula, Lam. Encycl. pi. 450. 

 f. 1 a h. 



G. testa haliotoidea, ovata, oblonga, dorso convexa, laevigata, 

 luteo-rosea, fusco-lineata ; spira laterali, subprominula ; labro sinu 

 arcuato. 



Shell haliotoid, ovate-oblong, convex on the back, smooth, yel- 

 lowish-rosy, with fuscous lines ; spire lateral, rather prominent ; 

 outer lip arcuated, sinuous. 



Eastern Seas, Celebes, etc. (Mus. Cuming.) 



2. Gena vauia (pi. clxxiii. f. 6, 7, 8), A. Adams, Pro. Zool. 

 Soc. Eeb. 1850. 



G. testa haliotoidea, ovato-oblonga, pohta, dorso sequaliter con- 

 vexa, latere sinistro striata, luteo, rubro alboque variegata ; spira 

 prominula, erecta, acuminata. 



A pretty little species, usually confounded with G. lutea, but 

 easily distinguished when its profile is examined ; the dorsum is 

 equally convex and polished, and the spire is rather prominent, 

 erect, and acuminated. 



Calapan, island of Miudoro; Aca})ulco; on the sands. Col. 

 Moffatt. (Mus. Cuming,) 



