Pvn H,i I'UitlS

ANOMIA. 29
* Mantle open and without tubes.
Family I. ANOMI'IDiE, (Anomiadce) Gray.
Body roundish : mantle having very thin edges, which are
furnished with fine and extensile tentacular filaments :
circular and double : foot
gills
small : muscle divided into two or
three parts, the largest of which passes through a hole in the
hinder part of the lower valve, serving for attachment to extraneous
bodies, and forming on them a fibrous or horny plug.
Shell generally circular and flat, more or less inequivalve :
a narrow slit :
orifice pear-shaped, being interrupted behind by
cartilage internal, short, placed somewhat obliquely below the
beak.
This family is connected with the Ostreida by the
genus Pododesmus of Philippi.
Dr. Leach proposed to
raise it to the rank of an Order, which he called
Trimya.
Genus ANO'MIA* Linne. PI. I. f. 4.
Body compressed.
Shell inequilateral, of an irregular shape, dependent on
that of the substances to which it is attached : upper valve
rather convex and thick: lower valve flat and thin: hinge
toothless.
As I have before observed, Fabius Colonna, the origi-
nator of this name, applied it to species of Terebratula.
About a centurv and a half afterwards Linne used it in
the same sense, for he described the animal as having
two arms, and the shell as furnished with two bonv
processes or radii, the deeper valve being often perforated
at the base. But he included in the genus
many species which we now recognize as belonging to
Anomia thus restricted, and long custom has sanc-
* Irregularity.