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 MY ARIA. 



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 MYA, Lin. 



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' ri a. 



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

 wrinkled eindcrmis ; 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. Nat., 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. Hrvg. , Encyc. Jlltth., pi. 229, f. 1 to 8. Blainv.; 



Malacol. ph 77, f. 1. Sowekbv; Ge?fC?-«, No. 33. Montagu j Test. Brit., 30. 



Wood; Gen. Conch., 91, t. 17, f. 3. Index, ■pi. 2, f. 2. Desha yes; Encyc. 



Mith., Fers, ii. 592, pi. 229, f. 1. Lam.; Jin. sans Vert. (Desh. ed.), vi. 74. 



Maton and Rackett; Lin, Trans., viii. 35. Tukton ; Condi. Diet., 98. Brit. 



Biv., 32. Donovan ; Brit. Shells, t. 85. Fleming ; Brit. Jinim. 403. Con- 

 rad ; Jlmer. Mar. Conch., 42, pi. 9, f. 1. 

 Mya mercenaria, Bay; Journ. Jlcad. JVat. 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. 



