t.r
-ii :; Family XVI. SOLE'NIDiE, Latreille.
Body elongated in a transverse direction : mantle closed in
front, with its borders adhering together, open at the anterior
end for the passage of a foot, and forming at the posterior end
two conical tubes or siphons of different lengths, which are
more or less enclosed in a common sheath : gills two on each
side, long and narrow : palps corresponding with the gills in
number and position, long, slender, and triangular : foot large
and muscular, adapted for burrowing in sand.
Shell shaped like the body, equi valve, open or gaping at
both ends: epidermis strong and persistent, overlapping the
front or ventral edges of the shell : heahs small : licjament external : hinge strengthened inside by a ridge : teeth consisting
of one or two thorn -like cardinals in each valve, which are
erect, curved, and interlock ; laterals partly recumbent, in
some cases rudimentary or wanting : muscular scars irregular
pallial scar sinuated.
This and the succeeding families of marine Conchifera
differ from those described in the second volume in
having the mantle more or less closed in front. Professor Oken imagined that^ in a biological point of view,
they typify the Nudibranchs and Salpse; but he gave
no reason for this fanciful analogy.
Although the
Solenidce appear at first sight to constitute a natural
and simple group, it will be found to comprise certain
forms which connect it with other families. This resemblance has probably misled some systematists, and induced them to associate with Solen such very dissimilar
genera as Psammobia, Lutraria, Panopcea, and Mya.
The structure of the hinge, however, will always serve
to distinguish any one of them from the rest.
Dr. Carpenter says that the external layer of the
shells in the present family is composed of cells which
VOL. III.
B