74 
fossils we are about to describe belong to the first divi- 
sion. 
This shell affords an excellent example of a continuous 
line of muscular impressions from the beaks along the line 
of attachment of the mantle, forming a complete circuit; 
they are very strong at the anterior edge, where they sup- 
port the powerful muscles of the cylindrical foot, the rapid 
action of which, when boring down into the sand, has been 
so often remarked ; the animal is said to descend some- 
times two feet perpendicularly with great rapidity. 
There are several recent as well as fossil species, all of 
which are littoral shells. Solen vagina , Linn., is the type 
of the genus. 
SOLEN gracilis. 
TAB. DCXLT.— fig. 1. 
Spec. Char. Transversely linear, seven times as 
wide as long, subcylindrical, slightly curved, 
smooth ; anterior portion separated by a direct 
furrow, small but rather wide, its upper mar- 
gin oblique ; the posterior extremity slightly 
rounded. 
This is a pretty shell, much like the Ensis ( Solen Ensis , 
Linn.) of the British shores, but it is more convex; its 
generic characters also distinguish it. It is one of the most 
interesting among the many discoveries of new shells made 
at the Barton Cliff by Mr. F. E. Edwards. Several spe- 
cimens were picked up. 
Fig. a. is an enlarged representation of the hinge. 
