MOLLUSCA. 
421 
Ancylus oblonga .— The Oblong Ancylus. 
Plate LXXXVII. fig. is. 
Aperture elongated, vertex turned to one side ; with fine con¬ 
centric strise ; pale horn-colour above, inside bluish. One-third 
of an inch long. Inhabits the fresh waters of Europe. 
Genus 15. — CREPIDULA.— Lamarck. 
Generic Character .—Head of the animal anteriorly forked, 
having two conical tentacula, with the eyes placed at their ex¬ 
terior base; mouth simple, destitute of jaws, and situated in 
the bifurcation of the head; branchiae with tufts and projecting 
from the branchial cavity ; the mantle never bordering the shell; 
foot minute ; anal orifice lateral; shell ovate, or oblong-ovate, 
convex on the back, and concave beneath; spire inclining to 
one side ; aperture with a horizontal partition next the spire, 
extending to nearly the middle of the shell. 
Crepidula aculeata. — The Prickly Crepidula. 
Plate LXXXVII. fig. 16. 
Oval, brown, with acute rough striae; vertex recurved; inside 
with a chamber, and bluish or purple. One inch long. Inha¬ 
bits the American seas. 
Genus 16—CALYPTRiEA.— Lamarck. 
Generic Character. —Animal unknown. — Shell conical, base 
orbicular, and summit vertical, imperforate and acute ; internal 
cavity with a spiral septum. 
Calyptrcea Sinensis .— The Chinese Calyptrh^a. 
Plate LXXXVII. fig. 19. 
Orbicular, subconic; vertex ending in a small volution ; 
smooth, margin entire; cream-yellow; very glossy within, and 
provided with a laminar plate. Three-fourths of an inch in 
diameter. Inhabits the Chinese seas. 
Genus 17.—PILE OP SIS. — Lamarck. 
Generic Character —Animal with two conical tentacula, and 
the eyes at their base; branchiae formed in a row under the an¬ 
terior margin of the cavity, near the neck.—Shell obliquely 
conical, anteriorly recurved, and the apex nearly spiral; aperture 
2 M 
