CONCHOLOGY. 33 
Shell. Sessile, univalve, rather globular, ventricose, convex 
above; apex perforated; aperture small, elliptical, operculum 
quadrivalve. Inhabits the Indian seas. One species. . 
Pyrgoma cancellata. 
7. Genus Anatifera. Pl. V. 
Animal. Body covered with a shell, supported by a long 
tubular tendinous peduncle ; with long, numerous, and unequal 
tentacular arms, which are articulated and ciliated, and emanating 
from the summit on one side. 
Shell. Compressed on the sides, with five flat valves, the valves 
contiguous and unequal; the lower lateral ones the largest: the 
whole of them united and kept together by means of their mem- 
branes. Inhabits the British seas. Six species. 
Anatifera levis. Anatifera dentata. 
A. villosa. A. striata. 
A. vitrea. A. aculeata. 
8. Genus Pollicipes. Pl. V. 
Animal. Body covered by a shell, and supported on a tabular, 
 tendinous, scaly peduncle ; with many tentacular arms. 
Shell. Consisting of thirteen or more valves, the smallest at 
the sides, which are very flat and compressed, the peduncle short, 
wrinkled, rigid, and often covered with scales like shagreen. 
- Inhabits the European and American seas. Six species. 
Pollicipes cornucopia. Pollicipes mitella. 
P. scalpellum. P. peronii. 
P, homii. 
P. Mortoni.* 
9. Genus Cineras. Pl. V. 
Animal. Body pedunculated, and encased in a membranous 
tunic, which is swollen above, with an opening below the summit, 
from which protrude many ciliated articulated arms. 
Shell. Composed of five testaceous oblong valves, two at the 
