MYA. 353 



Shell thick, strong, opaque, porcellanous, gaping poste- 

 riorly, valves usually unequal, covered with a wrinkled 

 epidermis. Hinge simple, toothless ; cartilage internal ; 

 cartilage-pit in a hollow process in one valve. 



Living in the sand or mud, lying on the side. 



The gills in this family are not prolonged into the bran- 

 chial siphon, nor is the body of the animal symmetrical. 

 The structure of the shell is cellular, with dark nuclei near 

 the outer surface, and the valves are usually invested with 

 a coarse wrinkled epidermis, which is continued over the 

 mantle and tubes of the animal. The siphons are either 

 wholly or partially retractile. The shells gape usually at 

 both extremities, and the cartilage is contained in a spoon- 

 like cavity at the hinge. 



Genus MYA, Linna3us. 



Shell oblong or rhomboidal, inequivalve, gaping at the 

 extremities, surface of valves striated or furrowed trans- 

 versely, and furnished with a wrinkled epidermis, beaks de- 

 pressed. Hinge composed of a dilated, ascending, spatulate 

 tooth in the left or smaller valve, with a corresponding socket 

 in the right ; cartilage short, thick, internal. Pallial impres- 

 sion deeply sinuated. 



Syn. Laternula, Bolten. 



Ex. M. arenaria, Linnaeus, pi. 95, fig. 1. Shell, M. 

 arenaria, fig. 1, a, 1, b. 



The " Gapers," as they have been termed, bury themselves 

 in the mud and sand in the low-water levels of the littoral 

 zone, and in the soft mud of bays and estuaries, ranging 

 from low-water to twenty-five fathoms. The species are few 

 in number, and principally affect the shores of northern 

 countries, being found in the Arctic Seas, Greenland, Sitka, 



