MYARIA. 



MOLLUSCA. MYA. 41 



slightly curved forwards, directly under which, in the left valve, 

 rises an erect tooth, rounded at its summit, of about equal breadth 

 and heidit ; its inner face is smooth and rounded ; its outer face 

 is divided into two portions, the largest of which is spoon-shaped, 

 the other flat and traversed across the middle by a grooved ridge 

 which projects beyond the margin of the tooth like a smaller tooth ; 

 on the right valve we have a deep excavation imbedded in the 

 cavity of the beak ; in this and in the concave portion of the 

 tooth is fixed the very strong cartilage ; anterior muscular im- 

 pression narrow and long, club-shaped ; posterior one semi-oval ; 

 palleal impression scolloped along the base, and very deeply 

 notched behind. Common length 3| inches, height 2 inches, 

 breadth 1 inch. I have a specimen, the corresponding dimen- 

 sions of which are 5|, 3y\, 2yV inches. 



This shell (the Clam) is familiar to every one who resides on the 

 sea-coast. It is always to be seen in every market, and on every quiet 

 shore. Its residence is always between high and low tide, or in such 

 places as allow it to be partially exposed to the air a part of the time. 

 Such are our sandy beaches, muddy inlets, and mouths of streams 

 emptying into the sea, &c. It usually lies just below the surface, 

 and over it is a round hole through which the animal occasionally 

 ejects a jet of water to a considerable height above the sand ; and, if 

 the shallow water is observed where they are known to dwell, it wdl 

 be perceived to be kept in constant eddies by the suction and ejection 

 of the water. The value of the clam as an article of food, in the 

 fisheries, and for manure, will be spoken of elsewhere. 



There seems to be no character which affords any ground for sep- 

 arating our shell from the European clam. Mr. Say, as he merely refers 

 to Pennant's figure, had probably never seen a specimen from the other 

 shore of the Atlantic. A comparison would certainly have saved him 

 from the error of describing it as a new species. Nor can I believe 

 there is any occasion to make two species, the mercenaria and acuta, 

 as he has done. His acuta was formed from a specimen in which the 

 posterior extremity was very acute ; but in this part we find great 

 diversity of proportions in different specimens. 



It seems not to be a common shell at the British Islands, and to be 

 seldom used as food there. 



Its surface is often colored by the earth in which it is found. Very 

 often it has a rusty color, or a bluish clay-color ; and the solidity of 



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