Page:American Seashells (1954).djvu/543

Rh coarse, concentric, irregular lines and with sharp, small, oblique, wavy threads. Uncommon offshore. Solecurtus sanctaemarthae Orbigny St. Martha's Razor Clam Plate 3oi North CaroHna to southeast Florida and the West Indies. % inch in length, differing from cinningiamis in being twice as long as high (instead of iV-j. times) and in having stronger sculpturing. Uncommon from shallow water to 2 5 fathoms. Super fa77nly MACTRACEA Family MACTRIDAE Key to Some Genera of Mactridae a. Ligament entirely internal Mulinia aa. Ligament partially external b. Chondrophore set off from ligament by a thin shelly plate: c. Posterior rostrate; shell thin and fragile .... La bios a cc. Both ends rounded; shell thick Mactra bb. Chondrophore not set off by a plate Spisula

Figure 89. Hinge of the Atlantic Fragile Mactra, Mactra fragilis Gmelin, 2 inches. Genus Mactra Linne 1767 Mactra fragilis Gmelin Fragile Atlantic Mactra Plate 32s; figure 89 North Carolina to Florida, Texas and the West Indies. 2 to 2 ^ inches in length, oval, moderately thin, but strong, and smooth- ish. Posterior slope with 2 radial, small ridges, one of which is very close to the dorsal margin of the valve. With a fairly large posterior gape. Color cream-white, with a thin, silky, grayish periostracum. A4oderately common in shallow water. Rarely reaches 4 inches in length. Mactra calijornica Conrad Californian Mactra Figure 9od Neeah Bay, W^ashington, to Panama.