34 CONCHOLOGY. 
sides of the aperture and three on the back, not covering the — 
whole of the body ; supported by a peduncle of a greenish colour 
with several longitudinal stripes. Inhabits the British coast. 
One species. 
Cineras vittata. 
10. Genus Otion. Pl. V. 
Animal. Body pedunculated, enveloped in a membranous 
tunic, which is ventricose above; two horn-like tubes, directed 
backwards, truncated, and open at their points, and situated in the 
apex of the tunic; having a Jateral opening, with many articulated 
and ciliated arms. 
Shell. Composed of two testaceous valves, attached near the 
lateral opening, the centre aperture admitting the animal’s tenta- 
cule, the singular form of which prevents its being blended with 
the genus cineras without a further examination of its structure. 
Inhabits the North seas. Two species. 
Otion Cuvieri. Otion Blainvillii. 
CLASS III. 
CONCHIFERA, 
Animal. Soft, inarticulated, always fixed in a bivalve shell, 
without head or eyes, having the mouth naked, concealed, and 
without any hard parts; a large mantle enveloping the whole of 
the body, forming two laminiform lobes; the edges detached or 
semetimes united in front. Gills or respiratory organs external, 
situated on each side between the body and the mantle ; circula- 
tion simple, the heart with one ventricle; some few ganglions of ; 
the different nerves, but no knotted medullary cord. 
Sheil. Always bivalve, enveloping the animal entirely or par- 
tially, sometimes free, sometimes affixed; the valves most. fre- 
quently united on oné side by a hinge or ligament. Sometimes 
attached to the shell are: testaceous accessory pieces. Twenty 
families. 
