102 



POPULAR COXCHOLOGY. 



calcareous, having a tooth-like process inside like that of 

 Nerita. Animal unknown. — 1 species ; also fossil. 

 Rissoina Inca is brought from Peru. 



Lacuna. Turton. — Shell turbinate, solid or thin, ob- 

 liquely conoidal, or subglobular, spire short or 

 produced, surface smooth (in the British species), 

 protected by an epidermis ; mouth ample, rounded, 

 peretreme entire, not continuous, outer lip sharp- Zacurui - 

 ened, columella lip expanded, grooved, umbilicated ; oper- 

 culum semicircular, corneous, of few rapidly increasing 

 whorls, the spiral nucleus lateral, and subterminal.* 

 Animal, having a muzzle-shaped head, with two long ten- 

 tacula, bearing eyes on bulgings at their external bases ; 

 no neck lobes ; operculigerous lobe expanded or winged 

 laterally, and furnished behind with two filamentary pro- 

 cesses, more or less developed, but sometimes nearly 

 obsolete ; foot rounded at both extremities, contracted 

 at the sides, centrally grooved ; branchial pliune single ; 

 lateral elements of the tongue heterogeneous, two of the 

 uncini, as well as the median denticle, with incurved (five) 

 denticulated apices.f — About 12 species; also fossil. 



Found on the shores of the Xorth Sea ; four British 

 >pecies, found principally on the northern shores. 



Fossarus. Philippi. fForsar Gray ; Maravignia, Ara- 

 das ; Phasianema Wood.) — Shell semi-globular 

 or egg-shaped ; umbilicated : aperture entire, gj^ J 

 semicircular : inner lip striated : operculum 

 horny, not spiral Animal, having the head 

 lengthened into a muzzle: two long tentacula, with the 

 eyes at the outer base, two frontal lobes : foot without 

 an appendage. — 2 species; also fossil. 



From the Mediterranean and Senegal. 



* Forbes's British Moll. t lb. 



