140 AMERICAN MARINE CONCHOLOGY. 
terior side ; cartilage process spatulate, in each valve, with an obsolete 
tooth in front, and a posterior lateral tooth ; pallial sinus very shallow. 
NERA. 
Genus MYA, Linneus. 
Syst. Nat., edit. x. 670. 1758. 
The animal has a small, straight, linguiform foot; the siphons 
are combined and covered with a partially retractile epidermis ; 
orifices fringed, branchial opening with an inner series of large 
tentacular filaments; gills not prolonged into the siphon ; palpi 
elongated, free. 
About ten species are known, of universal distribution. They 
are found in sand or mud, especially estuaries, and ranging, gene- 
rally, from low water to 25 fathoms. Our species are edible. 
1. M. anenaRIA, Linneus. Fig. 322. 
Syst. Nat., edit. xii. 1112. 1767. 
Mya acuta, Say. Journ. Philad. Acad., ii. 313. 1822 ( Young). 
Mya mercenaria, Say. Ibid. 
Shell transversely ovate, subequilateral, convex, gaping at both 
ends, but more so at the posterior end, where the valves curve 
outwards. Beaks small; epidermis rough, wrinkled, yellowish. 
Length 3 to 5 inches, height 1.5 to 2 inches. 
Inhabits the Whole Coast. (Hur.) 
Common everywhere, burrowing in sand between high and low 
water; its residence is readily detected by a small aperture in the 
sand, through which it ejects a stream of water upon treading hard 
on the surface. On many parts of Long Island the hogs are accus- 
tomed to root for this species, and follow the tides with unerring 
sagacily. 
2. M. rruncata, Linneus. Figs. 320, 325 (animal). 
Syst. Nat., edit. xii. 1112. 1767. 
Shell subquadrate, truncated behind, where it gapes widely; 
basal margin irregularly sinuous; epidermis tough and corrugated ; 
tooth broader than long, with a slightly thickened lobe on the edge; 
valves convex, beaks moderately prominent; epidermis yellowish. 
Length 2.5 to 3.5 inches, height 1.5 to 2.5 inches. 
Northern Coast. (Hur.) 
Externally, this common species resembles the Panopexa arctica, 
but is readily distinguished by its spoon-shaped tooth. 
