GASTEROPODA. 



125 



edge in its whole extent, which is repeated at equal 

 distances ; the inner lip is callous, and nearly covers the 

 entire columella. — Fossil. 



Separated from Dolium and Pterodonta by the absence 

 of a canal or notch, and from Globiconcha by the thick, 

 not thin lip. 



GrLOBiCONCHA. Z>' Orb. — Shell nearly globular ; spire 

 very short, even concave ; the aperture half-moon shaped, 

 curved at the base, without notch or canal ; the outer lip 

 thin, untoothed ; the columella without teeth or folds. 



Of this genus only fossil casts are known; but the 

 form is so striking that its proper place is soon perceived. 



Family 22. — PYRAMIDELLA CEA. 



The animals have a snout-formed flat head; two flat 

 ear-shaped tentacula, with eyes at the base ; the breathing 

 hole wide open, and there is only one gill ; a long pro- 

 boscis ; tongue unarmed, or only beset with rudimentary 

 teeth. The shell is turret-shaped, with many whorls ; the 

 aperture oval, entire; the inner lip perpendicular, and 

 often plaited ; operculum horny. — Marine. 



Pyramidella. Lam. — Shell turreted ; columella 

 having three plaits; outer lip thin, sometimes 

 furrowed within ; umbilicus small ; no epidermis. 

 Animal with a rounded foot, the border not 

 forked, the front assuming the form of a double- 

 lobed shield, and behind it has a furcation which 

 answers to the larger fold on the columella ; the 

 head is flat, broad, and deeply two-lobed; the 

 tentacula placed on the upper part, are acute, 

 ear-shaped, and as long as the head, with the eyes on 

 the inner side; operculum with an indentation on one 



