66 COyCHYLW—DITHYRA. 22. 



Chama fusca. Lister, Conch, tab. 415, fig. 2.5&. 



Mus. nosf. On sandy and muddy shores. 



Shell two Inches and a half long, and four and a half broad, 

 thin, brittle, nearly equally rounded at both the ends, covered 

 with a greenish or brownish wrinkled skin which projects three 

 or four inches beyond the extremity of the shell, and covers the 

 elongated tube of suction : both the sides slope nearly equally 

 from the hinge. 



Young shells are sometimes very much produced transversely, 

 but in all other respects similar. 



A singular variety, perhaps a distortion, is in our cabinet, in 

 which the valves are very unequal ; one of them being greatly 

 convex and larger, inclosing the other which is flat ; both of 

 them furnished with transverse plaits and striae, and on the inside 

 of the flat or smaller valve are raised laminar plates, especially 

 under the hinge: the cardinal margin runs in a nearly straight 

 direction ; the hinge is nearer to the more pointed end ; and it i« 

 barely an inch in length and two in breadth. 



It may possibly be the Mactra planata of Chemnitz, iv. p. 238, 

 tab. 24, fig. 2.38 and 2.39, who describes it as being furnished 

 with unequal plaits both inside and outside, and very finely 

 striated. It was dredged up in Torbay. 



