GLYCYMERI3. 



63 



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

 duabns obtusis," and the remark, that " externally it reseml^lcs Mya 

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

 be passed over as the toothless valve of Mi/a truncata. 



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 Panoixrn, although Wood- 

 ward and Hancock have shown that the aninud belongs rather to 

 Saxicava, and the ])allial impression consists also of a series ol 

 elongated dots as in that genus. 



Ociius GLYCYxlIEKIS, Lam. ISOl. 



Shell elongated, incquipartite, greatly gaping at both ends; 

 hino-e 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. 



Mi/n siliqua, CiiEMX. Conch. xi. 192, pi 198, lis. 1934. — Dillwy.v, Catal. i. 49. 



Gli/ci/meris incmssata, L.I.M. Syst. des An. sans Vert. 126. 



Glycymeris siliqua, Lam. An. sans Vert. 2d oil. vi. 09.— Blainv. Malac. pi. 80, fig. 3.— 



AuDOuiN, Ann. des Sc. Nat 18.33, pi. 14, 15, 16 (cxedlent). — SowERnv, Gen. 



of Shells, No. 8. — Desh. Encyc. Meth. Vers, ii. 171. — Chenu, Man. de Conch. 



i. 30, figs. 1-6. — Reeve, Elem. of Conch, ii. 161, fi.u'- 234. — Woouw. Man. of 



Moll. 320, pi. 21, fig. 14. — Stimpson, Shells of New England, 24. 

 Myapicen, WoOD, Gen. Conch. 96, pi. 22, fig. 5 ; Index, pi. 2, fig. 10. 

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



4, 4 a, 4 b. 



Shell long, oval, ])onderous, widely gaping at both ends, surface 

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

 horny, glossy-black c))idermis, which projects a considerable dis- 

 tance beyond the limit of the valves ; it is ol)li<iuely wrinkled at 

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

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

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

 calcareous substance, giving 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. 



