CONCHOLOGV. 39 



bly solid, with fine trenchant edges ; the summits very little 

 marked ; hinge dissimilar ; one or two oblique cardinal folds, diver- 

 gent, 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 coast. Four species. 



Mya truncata. Mya erodona. 



M. arenaria. M. solenimyalis. 



2. Genus Anatina. Pi. VL 

 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 seas. Ten species. 



Anatina lateina. Anatina trapezoides. 



A. truncata. A. rugosa. 



A. subrostrata. A. imperfecta. 



A. longirostris. A. myalis. 



A. globulosa. A. rupicola. 



FAMILY V. 



Mactracea. Seven genera. 

 1. Genus Lutraria. PI. VI. 



Animal. Body oval, much compressed, or subcylindrical ; 

 the mantle enclosed only in the half of its inferior side : foot 

 small and projecting but little beyond the abdominal mass, tubes 

 long, distinct or united. 



Shell. Oval or elongated, regular, equivalve, more or less 

 inequilateral, sometimes but slightly gaping ; edges always simple 

 and trenchant ; summits feebly marked ; hinge subsimilar, formed 

 by two very small divergent cardinal teeth ; two very distinct 

 muscular impressions united by a palleal impression profoundly 

 sinuous to the rear. Inhabits the seas of Europe. Eleven 

 species. 



