MACTRIDAE 445 



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. 



