the Family Osteodesmacea. — 145 
irregularly rounded, and situate near the superior ex- 
tremity ; they are both rather superficial, and connected 
by a palleal impression deeply and Dis indented 
posteriorly. 
Length two and a half, height one and three quarters, 
diameter one and a quarter inches. 
Oxgservations. Found living in the Mediterranean, 
and fossil in the Island of Sicily. It is believed that 
the only errors relative to.the synonymy of this species, 
are the reference to it by Mr. Conrad, in his American 
Marine Conchology, p. 44, as a synonym for the one found 
on our coast, and Kiener's misquotation of Mya distérta, 
Mont. This latter must have arisen from his deciding 
by an examination of the figures only, of Mr. Montagu's 
shell, as, had Kiener ever read any of the various de- 
scriptions of it, he would have been aware that one of 
the constant characters ascribed to it, is the anterior ex- 
tremity being rounded instead of truncated ; a dis- 
tinction sufficient, apart from its other peculiarities, to 
mark a specific difference. After a careful examination 
of the descriptions and figures of British authors, I feel 
convinced that T. corbuloides, Deshayes, does not 
exist, or at least has not been found, upon the coast of 
Great Britain. The description here. given is taken 
chiefly from M. Deshayes, with several additions, from a 
very fine specimen before me, of characters omitted by 
him. He describes the exterior surface of the valves as 
lisses, or smooth ; but this can only be the case where 
the granular asperities have been accidentally effaced, as 
it is not merely on the epidermis, but in the shell itself 
that these are visible when p S is fresh. In 
VOL. III.—-NO. II. 
H^. 
