ORDER TESTACEA. 119 
varies; the double tube forms a fleshy cylinder, and the foot 
is compressed. The different forms of the hinge have fur- 
nished Messrs. Daudin, Lamarck, &c. with the following sub- 
divisions, in the first three of which the ligament is internal. 
LUTRARIA, Lam. 
The lutrariz, like the mactre, have a ligament inserted into 
a large triangular cavity of each valve, and before this cavity a 
small chevron-formed tooth, but the lateral plates are wanting; 
the valves gape widely, particularly at the posterior extremity, 
through which passes the thick, double, fleshy, respiratory 
and anal tube, a disposition which attaches them to this 
family ; the foot, which issues at the opposite end, is small 
and compressed. 
Some of them are found in sand, at the mouths of rivers in 
France. (Mactra lutraria, List., &c.) In 
Mya, Lam., 
Or Mya proper, one valve is furnished with a plate which pro- 
jects into the other, furnished with a cavity; the ligament 
stretches from this cavity to that plate. 
Some species are found in the sand along the coast of 
France. (Mya truncata, Lin.) 
ANATINA, Lam. 
The anatine of Lamarck should be approximated to the 
preceding myz: each of their valves has a small projecting 
plate inside, with the ligament extending from one to the 
other. 
One oblong and excessively thin species is known, the valves 
of which are supported by an internal ridge, Solen anatinus, 
Chemn.; and another of a squarer form, without the ridge, 
Corbule, Encyc. 230—6. 
