30 



EAST COAST MARINE SHELLS 



reddish. 



An 

 men in Dr. 

 the Tortuga 

 The byssus, 

 80 mm. long 

 of brown, 

 at Sanibel. 



PI. 



Cap 



the 



exceptionally beautiful specl- 

 Perry's collection, taken on 

 s, measures 180 mm. in length, 

 which Is unusually silky, is 

 and in two contrasting shades 

 Single valves have been taken 



5, Fig. 1 

 e Hatteras, North Carolina to 

 West Indies 



GENUS ATRINA Gray 1840 



Valves unsulcate or without a mid- 

 way keel; the internal nacreous layer en- 

 tire. 



ATRINA RIGIDA Dlllwyn (Pinna muricata of 

 authors). Stiff Sea Pen. Shell somewhat 

 triangular, thickened; hinge line straight 

 or curved inward; mostly covered with low 

 radiating ribs which are smooth or with 

 scales, the scales elevated and often tubu- 

 lar in shape; ventral area smoother and 

 often with prickly scales; inner layer 

 dull brown and a little iridescent; color 

 dark brown or blackish. Length 6-9 inches. 



Dall has pointed out that the va- 

 riations are rarely associated, by the col- 

 lector, with the station where obtained. 

 They are short and wide when taken on hard 

 and stony ground, also with coarse irregu- 

 lar spines and distorted edges. On soft 

 bottom they are longer, spiny, or almost 

 smooth. The handsomest ones occur on clean 

 fine sand being beautifully developed and 

 perfectly preserved. 



PI. 5, Fig. 2 



North Carolina to South America 



ATRINA SERRATA Sowerby (Pinna seminuda of 

 authors) Saw-toothed Pen. Ribs very close 

 together, scales much smaller and more nu- 

 merous than in the preceding, also diminish- 

 ing in nvunber toward umbones. Length 6-9 

 inches. 



PI. 5, Fig. 3 



Cape Hatteras, North Carolina to 



the West Indies 



Family Pterlidae 



Shell very Inequivalve, right valve 

 with opening for attachment byssus. 



The "pearl oysters" which belong 

 to this family are found in Ceylon, Panama, 



and other warm seas. They are chiefly ex- 

 ported from Manilla. They afford both the 

 mother-of-pearl and the "oriental" pearls 

 of commerce. The Hope's Pearl, said to be 

 the finest in the world, measures 2 Inches 

 long and 4 around and weighs 1,800 grains. 

 From the days of Pliny the pearl fisheries 

 of Ceylon and the Persian Gulf have been 

 celebrated and furnish the most lucrative 

 trade. 



GENUS PTERIA Scopoll 1777; 

 Avicula, Lamarck 1799 (PEARL OYSTERS) 



PTERIA COLYMBUS Roeding (A. atlantica Lam.). 

 Shell fairly solid, convex; wing broadly 

 notched; smooth, usually brown, rayed with 

 light narrow bands with brown arrow-headed 

 spots. Length 3.5 inches. 



PI. 5, Fig. 7 



Cape Hatteras, North Carolina to 



West Indies 



GENUS PINCTADA Roeding 1798; 

 Margarltifera Humphrey 1797 (PEARL OYSTERS) 



Less oblique than the other Pteriae, 

 the valves flatter and nearly equal; right 

 valve with byssal notch and sinus near its 

 upper anterior part; valves winged; liga- 

 ment elastic. 



PINCTADA RADIATA Lamarck. Shell thin, in- 

 flated, somewhat oblique, winged at both 

 ends; surface ornamented with strong raised 

 rows of elongated scales, variegated with 

 colors; lateral teeth single in left valve 

 and double in right; interior nacre bright, 

 surrounded by a prismatic wide border. 

 Length 40 mm. 



Often the surface lacks the scales 

 referred to. These shells are sometimes 

 brought in by the Greek sponge divers of 

 Tarpon Springs, Florida. 



PI. 5, Fig. 6 



Georgia to the West Indies and 



Gulf of Mexico 



GENUS PEDALION Solander 1770; 

 Melina Katz 1788; Perna Brug. 1799 



Variable in form like Pteria; right 

 valve with byssal sinus; muscular impres- 

 sions inside double; hinge straight; no 

 teeth but with grooves where ligament is 

 fastened. 



