MACTRA. 367 



are stained for the most part likewise. In the more re- 

 cent specimens a tawny or yellowish brown closely-adhe- 

 rent epidermis somewhat obscures the vividness of the 

 radiation. The ventral margin, which is not particularly 

 arcuated, rises the more behind, where it forms a subangu- 

 lation with the produced and but moderately sloping pos- 

 terior dorsal, which edge is but very moderately convex in 

 the adult ; the hinder extremity is a little attenuated. 

 The anterior side is manifestly, though not very greatly, 

 the shorter, and tapers at the extremity (which is well, 

 but not symmetrically rounded) from the great declination 

 of the dorsal margin, the lips of which are pouting, but the 

 outline not in general arcuated. The umbones do not 

 greatly project, but incline a little forward ; the beaks are 

 blunt, not quite close to each other, and not preceded by 

 any concavity. The interior is whitish, or faintly exhibits 

 the external colouring ; the teeth are large and thin, and 

 the lateral laminse perfectly free from sulcation. 



The shell we have figured (which, being bleached by the 

 sun, is not so distinctly rayed as in the engraving, where 

 the colouring is restored from an exotic specimen) is about 

 the average size of those picked up on the English coast ; 

 foreign examples attain to the dimensions of four inches in 

 length and nearly three inches in breadth. 



The animal is figured by Poli, and appears closely to 

 resemble that of M. stuUorutn. Almost all the British 

 examples consist of the worn valves which were obtained 

 by Miss Pocock (1801) from the sands of Hale in Corn- 

 wall, and appear to have passed from her hands into the 

 cabinets of several collectors. It was from one of her spe- 

 cimens that Donovan, the original introducer of the species 

 into our Fauna, derived his figure and description. We 

 only know of two examples with the valves united ; these 



