CONCHOLOGY. . 91 
P, amena.* P. alveus.* 
P. alternata. * P. candida.* 
5. Genus Umbrella. Pl. [X. 
Animal. Body very thick and oval, provided with a dorsal 
shell ; foot large, smooth, and flat, surrounded by a border, ante- 
riorly notched, attenuated behind; head indistinct; four tenta- 
cula, the two upper ones thick, short, and truncated, the other 
two thin, and shaped like pedunculated crests; having foliaceous 
branchie. 
Shell. External, orbicular, subirregular, nearly flat, slightly 
convex above, white, with apex near the middle; margin acute, 
internal surface rather concave ; having a callous disk, coloured, 
depressed in the centre, surrounded by asmooth border. Inhabits © 
the Indian Ocean. Two species. 
Umbrella Indica. Umbrella Mediterranea. 
6. Genus Pleurobranchus. Pl. IX. 
Animal. Body creeping, fleshy ; mantle and foot expanded ; 
branchie placed on the right side; cloak enveloping the shell ; 
neck short, contracted in some species, with an emarginate front, 
exhibiting the commencement of the inferior tentacula, the upper 
ones tubular and cloven; gills at the edge of the dorsal plait, 
mouth provided with a short, retractile proboscis. 
Shell. Depressed, oval, oblong, concentrically wrinkled, almost 
entirely open, rounded and convoluted; the vertex with a single 
turn. Inhabits the coast of Devonshire in England Two 
species. 
Pleurobranchus Peronii. Pleurobranchus Laqueare. 
FAMILY IIL. 
Catyprracea. Seven genera. 
1. Genus Parmophorus. Pl. IX. 
Animal. Body creeping, thick, oblong ovate, broad behind, 
obtuse at the extremities ; border of the mantle cleft before, and 
