THE ASTARTES FAMILY ASTARTIDAE Shell equivalve, thick, triangular; surface ribbed; cardinal teeth two or three well developed; laterals obscure; ligament ex ternal, strong; pallial line entire.
Genus ASTARTE, J. Sby.
Shell heavy, sub-orbicular, closed, concentrically wrinkled or furrowed; epidermis thick; muscle scars two, kidney-shaped; foot tongue-shaped; mantle open; gills equal, oblique, united behind; siphonal orifices simple. About twenty species, bur rowers in muddy shores of northern seas. Nearly three hundred fossil species.
The Boreal Astarte (A. borealis, Chemn.) is rounded in outline, barely wider than long, somewhat flattened, the umbones a little nearer the anterior end. The surface is irregularly grooved with rounded ridges, becoming smooth toward the margins. The white surface is covered with an epidermis of yellowish brown. Walruses rake these mollusks out of the mud with their tusks, and swallow them whole. Length, i inch or more.
Habitat. New England to Arctic Ocean.
The Chestnut Astarte (A. castanea, Say) has its dorsal margin sloping up to the much elevated hinge, which, though almost median in position, yet turns decidedly forward. The concentric grooves are alternately strong and weak; a few faint radiating lines show through the chestnut-coloured epidermis. The animal's foot is bright red. Length and height, I inch.
Habitat. New England to New Jersey, British Isles.
The Flat Astarte (A. compressa, Montagu) roundish, flattened, with beaks elevated, and fine lines becoming obsolete toward the margin, occurs from New England northward. Length, inch.
370 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 Wavy 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, t 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, 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, 4 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. 371 The Astartes The inner margin of each valve is crenulated. Diameter, i to i i inches.
Habitat. New York northward.
Dr. Da11 puts this into sub-genus Venericardia, a name that im plies relationship with Venus and Cardium, and reports the species from the arctic seas to Cape Hatteras, in deep water. It is also found on the Pacific coast, from Alaska. Professor Keep describes a few closely related forms of Venericardia, all thick-shelled and from cold or very deep water.
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