A Be) CALYPTRAIDA. 
Shell conic, trochiform, spiral ; summit central ; whorls convex, 
plicate, not umbilicated; aperture large, containing a spiral 
transverse lamina, extending obliquely from the centre to the 
outer margin of the shell. The animal has an oblong foot, 
bilobed anteriorly. 
HALIOTIDEA, Swainson. Shell conic, spiral, the spire excentric, 
whorls convex, smooth, umbilicated. J. dtlatata, Sowb. (1xvi, 26). 
CALyptrR2&A, Lam. 
Cup and saucer limpet. 
Syn.—Cemoria, Risso. Mitrella, Trochilina, Trelania, Pocu- 
lina, Gray. Mitrularia, Schum. Lithedaphus, Owen. 
Distr.—Temperate and tropical; world-wide. C. Martiniana, 
Reeve (lxvi, 27). 
Shell conical, more or less regular, with subcentral, subposte- 
rior sharp apex; aperture basal, with a central lamina, half cup- 
shaped, attached to the apex and open in front. 
Animal with broad muzzle; tentacles rather short, lanceolate ; 
eyes on bulgings at the outer bases of the tentacles ; mantle- 
margin simple, sides plain. 
CrucispuLuM, Schum., 1817. 
Syn.—Bicatillus, Biconia, Swains. Siphopatella, Lesson. Tre- 
lania, Neleta, Gray. 
Distr.—Temperate and tropical; world-wide. C. rudis, Brod. 
(Ixvi, 28). 
Differs from Calyptrea in the internal cup-shaped lamina, 
which is entire and attached along a line on one side to the inner 
wall of the shell. 
DISPOTHA, Say. (Calypeopsis, Lesson.) Cup-shaped lamina 
adhering to the whole of one side. C. striata, Say \1xvi, 29). 
CATILLINA, Gray. Oblong, conical, radiately ribbed ; the apex 
acute, subcentral, recurved; nucleus regular, spiral; cavity 
conical, with a broad trigonal cup on the left side under, but not 
extending to the apex of the cavity, filled with a callous deposit 
at the tip; the part of the cup next to the inner surface of the 
shell scarcely thickened and not raised up. Crucibulum conca- 
merata, Rve. (lxiv, 77). ; 
CREPIDULA, Lam. 
Etym.—Crepidula, a small sandal. 
Syn —Crypta, Humph. Sandalium, Schum. Crepipatella, 
Lesson (7). Tylacus, Lyroscapha, Conrad. 
Distr.—50 sp. West Indies, Atlantic and Pacific Coasts of 
N. America, Mediterranean, W. Africa, India, Australia. C. 
Peruviana, Lam. (lxv, 91). Fossil. Cretaceous—. 
Shell oval, limpet-like, with a posterior, generally lateral spiral 
apex; interior with a shelly lamina covering its posterior half. 
