TRACHELIPODA. 97 



FAMILY V. lANTHINEA. 



Shell not floating, having the aperture very wide; no 

 columella. 



Genus 54.— lANTHTNA.— Za/narcA. 



Generic Character. — Shell ventricose, somewhat conical, 

 thin, and pellucid ; aperture triangular ; columella straight, 

 produced beyond the base of the outer lip, which has a 

 sinus in the middle aperture without an operculum. 



lanthina communis. — The Comjion Ianthina. Plate 

 XII. fig. 19. Extremely fragile, of a beautiful violet hue; 

 aperture triangular, with a small notch on the margin of 

 the outer lip. One inch long. Inhabits the Atlantic and 

 Mediterranean. 



FAMILY VI. NERITACEA. 



The shells are both marine and fluviatile ; semiglobular 

 or oval ; destitute of a columella, with the aperture edged 

 and transverse, and provided with an operculum. 



Genus 55.— ^kTlCk—Adanson. 



Generic Character. — Shell subglobose, umbilicated; aper- 

 ture entire, and half rounded ; inner lip oblique, without teeth ; 

 but having a callosity, which partly covers the umbilicus, 

 and in some species entirely conceals it ; outer lip sharp, 

 smooth within ; aperture provided with an operculum. 



Natiea Canrena. — The Canrene Natica. Plate XII. 

 fig. 15. Subglobular, smooth; fawn-coloured, with bands 

 and interrupted rays of reddish-brown, and zigzag lines and 

 streaks; base of body and inner lip white, deeply umbili- 

 cated ; spire a little prominent. One inch and three-fourths 

 long. Inhabits the West Indian ocean. 

 I 



