40 INVERTEBRATA OF MASSACHUSETTS. 



accordingly, it is not difficult to obtain specimens through the fishermen. 

 In young shells the epidermis is smooth, and of a light chestnut- 

 color. 



FAMILY MYARIA. 



Shell often inequivalve, inequilateral, gaping ; hinge with an erect, more or 

 less spoon-shaped tooth in one valve, received into a corresponding excavation 

 in the opposite valve, united by an interposed cartilage. 



GENUS MY A, Lm. 



Shell transverse, gaping at both ends; left valve with a single 

 broad, compressed, erect tooth, received into a pit in the opposite 

 valve. 



MYA ARENA' RIA. 



Shell transversely ovate, chalky-white, covered with a thin, 

 wrinkled epidermis ; tooth of equal length and breadth, inclined 

 a little backwards and inwards, with an oblique rib on the back. 



State Coll., No. 234. Soc. Cab., No. 1722. 



Mya arenaria, LIN. ; Syst. JVa., 1112. PENNANT ; Brit. ZooL, iv. 79, t. 42, 

 f. 16. CHEMN; Conch., vi. 10, t. 1, f. 3, 4. FABR. ; Fauna Grcenl., 405. 

 DILLWYN; CataL, i. 42. DRUG., Encyc. Mtth., pi. 229, f. 1 to 8. BLAINV. ; 

 MalacoL pi. 77, f. 1. SOWERBY; Genera, No. 32. MONTAGU; Test. Brit., 30. 

 WOOD; Gen. Conch., 91, t. 17, f. 3. Index, pi. 2. f. 2. DESHAYES; Encyc. 

 Meth., Vers, ii. 592, pi. 229, f. 1. LAM. ; Jin. sans Vert. (Desh. ed.), vi. 74. 

 MATON and RACKETT; Lin. Trans., viii. 35. ,TURTON ; Conch. Diet., 98. Brit. 

 Biv., 32. DONOVAN ; Brit. Shells, t. 85. FLEMING ; Brit. Anim. 463. CON- 

 RAD ; Amer. Mar. Conch., 42, pi. 9, f. 1. 



Mya mercenaria, SAY; Journ. Acad. Nat. Sc., ii. 313. 



Mya acuta, SAY ; Ibid. 



Shell ovate, equivalve, nearly equilateral, moderately thick, 

 gaping at both ends, especially at the posterior, which cannot be 

 closed on account of an outward curvature of the valves ; an- 

 teriorly shortest and regularly rounded ; posteriorly narrowed and 

 rounded ; surface wrinkled, and in some parts raised into ridges 

 at the lines of growth ; faint radiating lines and colors depart 

 from the beaks ; color dingy-white, covered with a very thin, 

 dirty-brown epidermis, irregularly wrinkled ; beaks small, pointed, 



