290 DIMYARIA.—MYAD&. 
ing in it the Solenide@ already described, as well as 
the genera of which Messrs. Forbes & Hanley con- 
stitute the three families Myade, Corbulide, and 
Pandoride ; the British representatives of the last- 
named two are few, and for the most part small, 
though remarkable for the curious form of the shell, 
which projects at one side as if distorted. 
The shell in the MWyade is nearly regular and 
equal-valved, oblong, and somewhat coarse in 
appearance, gaping at the two extremities. The 
hinge is incomplete, the teeth being gradually 
effaced, but generally composed of one or two ob- 
lique diverging folds. The ligament is sometimes 
internal, sometimes external. There are two dis- 
tinct muscular impressions connected by a pallial 
impression, widely sinuated behind. The animal 
is compressed, becoming in the different genera 
more and more cylindrical, as well as more com- 
pletely closed, and prolonged backwards into two 
long siphons, which are ordinarily united, with 
fringed extremities. In front, the mantle allows 
the protrusion of a very small foot. The gills are 
narrow, free, and prolonged into one of the siphons. 
All the animals of this family live plunged in 
the mud or sand, which is ordinarily covered by 
the sea. They rarely change their place or their 
position, invariably being vertically immersed, with 
the siphons above and the foot beneath. Many of 
the species grow to a large size, and as they are 
both wholesome and palatable, they are on some 
coasts much prized for the table. 
GENUS MYA. 
The hinge in this genus is composed of one or 
two oblique folds, diverging backwards from a 
