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 Otlo7i. PI. 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 lateral 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- 

 culse, 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 Blainviilii. 



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 

 sometimes 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. 



Shell. Always bivalve, enveloping the animal entirely or par- 

 tially, sometimes free, sometimes affixed ; the valves most fre- 

 quently united on one side by a hinge or ligament. Sometimes 

 attached to the shell are testaceous accessory pieces. Twenty 

 families. 



