GLYCYMERIS. 53 



which, indeed, bears evidence of entire maturity. The " costis 

 duabus obtusis," and the remark, that " externally it resembles Mya 

 truncata," are enough to identify the shell. A single valve would 

 be passed over as the toothless valve of Mya tnincata. 



It is an interesting shell on account of the genus being found 

 plentifully on both continents in a fossil state, while recent speci- 

 mens are so rare. 



[I have retained this shell in the genus Panopaai, although Wood- 

 ward and Hancock have shown that the animal belongs rather to 

 tSaxicava, and the pallial impression consists also of a series of 

 elongated dots as in that genus. 



Ocmis OLYCYilIEBIS, Lam. 1801. 



Shell elongated, incquipartite, greatly gaping at both ends; 

 hinge margin callous, without a tooth ; ligament external, epider- 

 mis thick, extending beyond the margin of the shell. 



Glycymeris siliqua. 



■ Shell elongated, oval ; epidermis black, dense, and shining, obliquely wrinkled ; 

 beaks eroded; interior loaded with thick callus. 



Afya siliqua, Chemn. Conch, xi. 192, pi. 198, fig. 1934. — Dillwyn, Catal. i. 49. 



Gli/cijmeris incrassata, Lam. Syst. des An. sans Vert. 126. 



Glycymeris siliqua. Lam. An. sans Vert. 2d ed. vi. 69. — Blaixv. Malac. pi. 80, fig. 3. — 



AuDOuiN, Ann. des Sc. Nat 1833, pi. 14, 15, 16 (excellent). — Sowerry, Gen. 



of Shells, No. 8. — Desk. Encyc. Mcth. Vcr.*, ii. 171. — Chenu, Man. de Conch. 



i. 30, figs. 1-6. — Reeve, Elcm. of Conch, ii. 161, fig. 234. — Woonw. Man. of 



Moll. 320, pi. 21, fig. 14. — Stimpsox, vShells of New England, 24. 

 Mya picea, Wood, Gen. Conch. 96, pi. 22, fig. 5 ; Index, pi. 2, fig. 10. 

 Cyrtodaria siliqua, Woodw. Ann. and Mag. xv. 99. — Adams, Gen. ii. 352, pi. 94, figs. 



4, 4 a, 4 6. 



Shell long, oval, ponderous, widely gaping at Iwth ends, surface 

 undulated at the different stages of growth ; covered with a thick, 

 horny, glossy-black epidermis, which projects a considerable dis- 

 tance beyond the limit of the valves ; it is obliquely wrinkled at 

 various parts, especially at the posterior end ; beaks not promi- 

 nent, always more or less eroded ; ligament large and protuber- 

 ant ; interior of the shell white, loaded with a very thick mass of 

 calcareous substance, givhig the shell great weight, its margin 

 having a somewhat fringed arrangement. Height, one and one 

 half inches ; length, three and one half inches ; breadth, one inch. 



