40 CONCHOLOGY. 
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FAMILY IV. 
Myanrra. Two genera. 
1. Genus Mya. PI. VI. 
Animal. Subcylindrical, enveloped in a mantle pierced only 
with one interior and inferior hole for the passage of a very small 
-and conical foot; the tubes very considerable, and completely 
united; a tolerably large mouth, oval, and with simple lips; 
very small labial appendages: branchial lamine inconsiderable ; 
the external very short, the internal united with that of the oppo- 
site side. 
Shell. Surrounded with a thick epidermis, which is prolonged 
upon the tubes and the edges of the mantle of the animal; tolera- 
-bly solid, with fine trenchant edges; the summits very little 
marked ; hinge dissimilar; one or two oblique cardinal folds, di- 
vergent, behind a horizontal spoon-shaped hollow upon the left 
valve, corresponding with a hollow; horizontal and cardinal in 
the right valve ; two distinct muscular impressions. Inhabits the 
British and American coasts. Eight species. 
Mya truncata. Mya erodona. 
M. arenaria. M. solenimyalis. 
M. hyalina.* _ M. acuta.* 
M. canceliata.* M. mercenaria.* 
2. Genus Anatina. Fl. VI. 
Animal. Unknown. 
Shell. Transverse, subequivalve, gaping at both valves, or in 
one only; no cardinal teeth; one broad primary tooth in both 
valves, projecting interiorly ; a lateral plate running obliquely 
under the primary teeth. Sometimes there is a fissure extending 
from the apex, giving the appearance of a second plate or rib. 
Inhabits the British and American seas. ‘I'welve species. 
Anatina laterna. Anatina trapezoides. 
A. truncata. A. rugosa. 
A. subrostrata. A. imperfecta. 
