49 
fi- 
SOLEN. 
(See Plate IV. Fig. 4 and 5.) 
Shell oblong, gaping at both ends. Tooth of 
the hinge subulate, reflex, often double, not in- 
serted. (Fig. 3.) Lateral margin obsolete. 
The valves are convex, and in some of the more 
oval species, the beaks, which are mostly obsolete, 
are short and incurved. 
In a few species there is an internal rib extend- 
ing from the hinge to the margin of the cavity in 
a longitudinal direction. The disproportionable 
breadth of the shells in this genus is a remarkable 
character, and many of them are extremely 
brittle. 
The form of the solen is extremely well adapted 
to the motions of the animal which it contains ; 
these being exclusively in a perpendicular direc- 
tion. It makes its way through the sand of the 
sea-shore, to a certain depth, and thence again 
to the surface to seek for food. This is a tribe 
which can hardly be confounded with any other. 
E 
