MYTILIDAE 



349 



Glycymeris americana DeFrance Giant American Bittersweet 



North Carolina to north Florida to Texas. 



Up to 5 inches in length, rather compressed, always much flatter than 

 imdata. The dorsal or hinge side of large specimens is quite long. Beaks 

 point toward each other and are located at the midpoint of the hinge. Color 

 drab-gray or tan, rarely with weak mottlings. Rare. 



Glycymeris subobsoleta Carpenter 



Aleutian Islands to Lower California. 



West Coast Bittersweet 



Plate 3ie 



I inch in size, subtrigonal, texture chalky. Periostracum velvety, but 

 usually worn away. Ligament area short. Radial ribs flat, with narrow inter- 

 spaces; usually white, but may be with light- to medium-brown markings. 

 A rather common shallow- to rather deep-water species. 



SEPTIFEK 



milLUS 



VOLSELLft BRACHI00NTE5 



Figure 74. Hinges of some genera of mussels. 



Suborder ANISOMYARIA 

 Superfamily MYTILACEA 



Family MYTILIDAE 

 Genus Crenella Brown 1827 



Shells small, oval to oblong-oval, thin, brownish periostracum and with 

 fine decussate radial ribs. Ligament weak, internal. Margins crenulated. In- 



