The Astartes 



A. depressa, Brown, with its beak depressed, and valves 

 convex, has its concentric ridges squared, and the grooves be- 

 coming obsolete on the umbones and near the posterior margin. 

 Length, over i inch. 



Habitat. — Maine northward, Arctic Seas of Europe. 



The V/avy Astarte {A. undata, Gld., A. sulcata, Da C.) is 

 a handsome, well-marked species, the concentric wavy ridges 

 distant, the epidermis thick and brown. The blunt beaks are 

 drawn forward and meet over the hinge line which is crenulated. 

 Length, i^ inches. 



Habitat. — New England to Cape Hatteras. 



The western species range from Behring Sea tO Puget Sound. 

 All are small, roundish, with characteristic concentric furrows 

 and elevated beaks. 



The Polar Astarte {A. polaris, Dall) has a shining pale 

 brown epidermis overlying a series of fine ridges. Length, i ^ 

 inches. 



Habitat. — Alaska, Greenland. 



The Alaska Astarte (A. Alaskensis, Dall) is white with black 

 periostracum over coarse furrows. Length, 2 inches. 



The Esquimalt Astarte {A. Esquimalti, Baird) has broad 

 flat ridges that branch irregularly. Length, f inch. 



Habitat. — Puget Sound, northward. 



The Varnished Astarte {A. vernicosa, Dall) has five ridges 

 covered with a shining yellowish brown epidermis. Length, | 

 inch. 



Habitat. — Behring Sea. 



Genus CARDITA, Brug. 



Shell round or oblong, radiately ribbed; margin toothed; 

 hinge teeth two, strong, with an additional elongated posterior 

 tooth. Mantle margins free except between siphonal orifices; 

 incurrent tube with conspicuous fringe; foot rounded and grooved, 

 spinning a byssus; gills rounded in front, tapering behind, united, 

 outer pair narrowest. 



The Northern Cardita (C. borealis, Conr.) is nearly round 

 in outline, with broad, rounding ridges curving from the forward- 

 pointing beaks. A rusty epidermis dips into the narrow sulci. 



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