168 TESTACEOUS MOLLUSCA. 
very fine transverse striz, the dorsal margin carinated, the keel 
erenulated. 4..12.—X¢pixapi. 
* * Postrated. 
N. Arctica. Brod. Z, J. 4. t. 9. f. 1. Oblong, anteriorly 
subrostrated, the beak slightly recurved posteriorly longer and 
somewhat rounded; epidermis thick shining and dark olivaceous ; 
the delicate lines of growth crossed centrally and anteriorly by 
strong oblique strie. 7,..13.—Kamskatchka. The edge of 
the anterior slope forms a sharp elevated ridge when the valves 
are closed. 
N. Nicoparica. Lam. 4.—C. I. f. 4.—Reeve. t. 85. f. 4.— 
Arca Pexuucipa. Gimel. 3308.—W. t. 9. f. 26.—A. Levi- 
cata. D. p. 237.—Ch. f. 541.—L. t. 309. 7. 8. Transverse, 
ovate-elliptic, or ovate oblong, anteriorly subangulated, thin, smooth 
yellowish, pellucid, obtuse at the extremities but anteriorly rather 
attenuated: margin entire. 1.—Jndian Ocean. 
N. Rosrrata. Turt. B. p. 178.—Arca R. Mont. Sup. 
t. 27. f. 7.—D. (in part.) p. 245. Oblong, thin, pellucid, white, 
smooth, rather gibbous ; posterior side rounded ; anterior acumi- 
nated, turned upward, with three crenated ridges; surface covered 
with oblique nearly longitudinal grooves, margin entire. 2..4'5.— 
Guinea, Sc. 
N. Petua. Lam. 3.—Son. G. f. 4.—C. I. f. 6.—Reeve. 
t. 85. f. 6.—Arca P. Lin. 1141?—D. p. 237 ?—Ch. f. 546 ?’— 
W.t. 9. f. 27.—N. Srriata? Philippi. p. 64. Transversely 
ovate subtriangular, subequilateral, yellowish olive, thin, pellucid, 
with regular transverse grooves: posteriorly rounded, anterior 
dorsal edge but little if at all incurved and forming a sharp angle 
with the scarcely arcuated ventral. 2%..3.—Mediterranean. 
N. Fuuviatinis. Sow. G. f. 3.—Arca F. Sehro. Flus. 
t. 9. f. 2.—Ch. f. 550, 1.—H#. t. 309. f2 7.—N. Rosrrata. 
Lam. 2.—Arca RR. Gmel. 3308.—(in part.) D. p. 245.— W. t. 
Jf. 43.  Transversely oblong, rather convex, thin, transversely 
striated, posterior side rounded and more than twice as short as 
the anterior which is attenuated beaked and its very narrow ex- 
tremity obtusely angulated; anterior dorsal line nearly straight, 
oblique: ventral edge rather arcuated. 3..14.— Baltic, N. Seas. 
N. Minvuta.* Turt. B.p. 178.—Arca M. Gmel. 3309.— 
Mont. p. 140.—D. p. 245.—W. t. 10. fi 44.—A. Caunpara. 
Don. t.78.—TEnvuisutcata. Couth. (fide Gould.) Oval, trans- 
versely striated, white, with three or four concentric ridges, the 
anterior side produced curved and truncated: beak very small 


1 This is not the Arctica of Gray in Parry’s voyage. 
