MYOCONCHA. 
Gen. Char. A very unequal sided, but equal* 
valved, oblique bivalve ; hinge with an ex- 
ternal ligament, and one elongated, oblique 
tooth in the left valve ; beaks close to the 
posterior extremity ; no sinus in the impres- 
sion of the mantle. 
A very remarkable Genus, in general form resembling 
Modiola, but bearing a close affinity to Astarte (Crassina 
Danmoniensis Lam.) and the Conchae generally of 
Lamarck. The support of its hinge Ligament* is very 
prominent ; it has no lateral teeth ; the posterior side or 
lobe is almost wanting ; the surface has no ribs ; the 
three last characters distinguish it from Cardita, the im- 
pression of the posterior muscle is deep. 
Only one species is known. The Generic name im- 
plies its resemblance in form to a Mouse or Muscle, 
together with its affinity above alluded to. 
MYOCONCHA crassa. 
TAB. CCCCLXVH. 
Spec. Char. 
Shell ovate, slightly curved, pointed at one end, con- 
vex, nearly smooth, thick in substance : in the young 
state there are 3 or 4 longitudinal elevated striae, crossed 
* I propose to call this part the fulcrum , in place of a term generally 
considered objectionable, and also because it may apply to the same part 
whether it be elevated or not. 
