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 ^Vavy 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, ij 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. folaris, 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, | inch. 



Habitat. — Puget Sound, northward. 



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

 covered with a shining yellowish brown epidermis. Length, f 

 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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