TRIBE OSTRACEA. 313 



foreign substances, seemingly ribbed, tuberculated, &c, but never 

 with sculpture regularly radiating from the beaks), white, orange- 

 yellow or reddish violet : perforation for the most part large : sub- 

 central scars 3, the upper large, the two others rather smaller, 

 subequal, one ajbove the other, the lower of the two rather more 

 behind. 2£. Europe. 1 Var. ? from New York. Upper valve 

 wholly or partially yellow ; lower valve green. Looks like Philippis 

 figure of A. Peruviana (N. C. 3, An. t. 1,/. 2, 3). 



A. Aculeata.* Mul.—Gm. 3S±G.—Bru<f. 73.— Mont. 157, t. 4, 

 /. 5.— Gould, Mas. p. 139,/. 90.— Brit. Mar. C.f 73.— Brit. Mol. 2, 

 p. 332, pi. 55, /. 4. — A. Striolata, Turt. B. p. 233. Suborbicular, 

 resembling the last species, but small, never coloured either within 

 or without, and always armed in one or both valves, with most 

 crowded series of prickly striae, which emanate from the beaks, and 

 radiate most regularly to the margin. 2 ' £. Britain, dc. 



A. iExiGMATicA. — Tellina M. Ch.f. 1949, 50. — A. Rosea, Gray, 

 Ann. Ph. 1825.— A. M. Wieg. Arc. 1837.— Gray, Cat. An. p. 20.— 

 tExigma R., Kust. Ch. vii. pt. 1, t. 7,f. 1 to 7. Transverse, oval or 

 oblong (more rarely cylindraceous), thin, compressed. Upper valve 

 of an uniform purple or more rarely yellow tint, smooth, or with a 

 few obsolete radiating ribs ; apex acute, considerably within the dorsal 

 edge, a rudimentary linear notch in the margin above it ; upper sub- 

 central scar rather large, the two lower ones smaller, equal-sized, 

 nearly confluent. Lower valve very much paler ; perforation small, 

 remote from the edge ; one lobe overlapping the other. 1£. Singa- 

 pore; Philippines. 1 



A. Lampe. Gray, Z. P. 1 849, p. 117; Cat. An. p. 19. — Carpenter, 

 Mazatlan Shells, p. 167. Thin ; upper valve yellow (rarely salmon- 

 coloured), radiatingly ribbed ; apex submarginal ; lower valve white, 



1 The two following, with the A. Pectixata of Bruguiere (Ch. 698, 

 690), and his A. Striatula (for Ch.f. 697), are probably forms of the 

 same polymorphous shell : — 



A. Membraxacea. Lam. 7. — E. t. 170, /. 1, 3? Rounded, flat- 

 tened, so excessively thin as to be almost membranaceous : back of 

 the larger valve yellowish, obsoletely ribbed. 1^-. 



A. Lens. Lam. 9. Minute, obliquely elliptic ; pierced valve a 

 little convex ; perforation small, oblong ; umbo of the other valve 

 acute. Europe. 



2 Philippi regards the A. Aculeata of Loven as a distinct 

 species, and has termed it A. Venusta {N. ('. 3, An. t. \,f 5). 



3 Compare with this the ^rEx. Reticulatum, Corrugatfm and 

 Ooxvexum of Koch, in Kust. Ch. vii. pt. 1, t. 7. 



z 



