32 



EAST COAST MARINE SHELLS 



OSTREA VIRGINICA Gmelin. Virginia Oyster. 

 Upper valve smaller, flatter and smoother 

 than the lower; leaf -like scales upon sizr- 

 face; muscular impression central. 



In northern waters this oyster at- 

 tains a length sometimes of a foot, being 

 long, narrow and tongue-like in shape. The 

 swinging aerial roots of the mangrove af- 

 ford it support in the West Indies. When 

 living under flat stones and on timber it 

 often assumes a circular shape. 



PI. 6, Fig. 4 



Prince Edward Island to the West 



Indies 



Family Dimyldae 



Shell inequilateral, inequi valve, 

 closed; upper or left valve slightly small- 

 er, lower attached to some object; liga- 

 ment minute; hinge short, straight. 



GENUS DIMYA Renault 1848 



DIMYA ARGENTEA Dall. Shell white, silvery 

 outside; interior white, brilliant, porcel- 

 laneous. Length 10.5 mm.; height 12 mm. 

 Range 73-248 fathoms. 



PI. 62, Fig. 5a-b 



Off North Carolina to West Indies 



Family Spondylidae 



GENUS SPONDYLUS Linne 1758 

 (SPINY OYSTERS) 



Shell irregular, attached by right 

 valve; ribbed, spiny or foliaceous surface; 

 umbones far apart; lower valve with trian- 

 gular hinge area; hinge of two curved in- 

 terlocking teeth in each valve. 



The lower valve is usually spiny 

 and less colored. Some of the species are 

 found half embedded in coral reefs. The 

 Gulf of California is the home of many 

 ornate forms but the species are never 

 strictly local and are widely dispersed. 

 They are popularly known as Chrysanthemum 

 shells on account of the form and vivid 

 red or yellow color. 



SPONDYLUS AMERICANUB Hermann. (S. spathul- 

 Iferus Sby. and S. echinatus Martyn) . Shell 

 brown, purple, white, or red with well- 

 defined border inside; scales of principal 

 ribs narrow and erect at base, ribs between 

 with smaller scales; umbones often varie- 



gated with red. Length 2-6 inches. 



The largest examples occur in the 

 Gulf of Mexico. The frequent crimson col- 

 or is very striking and single valves, in 

 consequence, are conspicuous objects upon 

 the beaches. 



PI. 6, Fig. 1 



PI. 54, Figs. 1, 4 



Cape Hatteras, North Carolina to 



the West Indies 



GENUS PLICATULA Lamarck 1801 

 (PLAITED SHELLS) 



Shell irregular; attached by umbo 

 of right valve; two hinge teeth in each 

 valve locking into corresponding hollows 

 in each valve; muscle scar simple. 



PLICATULA GIBBOSA Lamarck (P. ramosa 

 Lamarck) Humped Plait Shell. Shell solid, 

 with pale yellow or white raised folds; 

 sometimes with short gray or red lines; 

 fan-shaped, with strong radiating and of- 

 ten dividing plications which terminate in 

 a saw-toothed margin. Length 1 inch. 



The dark venous lines are some- 

 times replaced with a brownish blush. 



PI. 6, Fig. 5 



Cape Hatteras, North Carolina to 



the West Indies 



Family Pectinidae 



Animal with mantle quite open, 

 double margined, inner pendant-like cur- 

 tain finely fringed, at Its base a row of 

 conspicuous round black eyes. 



The yoving Pecten spins a byssus 

 which is used as an attachment to some 

 stationary object. The notch or opening 

 in shell permits manipulation of the byssus 

 without opening of the valves. 



Adults, usually, are free swimmers 

 and the same applies to the fry. They pro- 

 pel themselves through the water by rapid- 

 ly opening and closing the valves. 



A Mediterranean form P. jacobaeus, 

 St. Joseph's shell, was worn by pilgrims 

 to the Holy Land as a badge of several or- 

 ders of Knighthood. 



More than two hundred and fifty re- 

 cent species are known, twice that number 

 fossil. 



