TRIBE OSTRACEA. sy a) 
frequently brown, the umbo usually smooth and within bluish green, 
apex rather within the dorsal margin; subcentral scars 2, the upper 
one oblong, very large; the lower one small, roundish, on the lower 
part of the hinder margin of the upper one: a dull triangular hollow 
above the great perforation. 14. Britain, de. 
A. Srriara.* Loven, Ind. Sean.— Brit. Mol. 2, p. 336, t.55, f. 1, 6, 
and t. 53, f. 6.—? Squama Maewna, Ch. 697 (from which A. S., Gm. 
D. p. 290, and W. t. 11, f. 11), copied EH. t. 171, f. 22, 3. More or 
less orbicular, resembling the last, but with most crowded rows of 
regular minute radiating, yet not prickly, scales, in place of ribs: 
often rayed with ferruginous-brown.' 1, North Britain, de. 
A. Cuminem.—Pracuanomia C. Brod. Z. P. 1832.—Sow. G.— 
Penny Cyc. 17, p. 364.—Reeve, t. 128.—Gray, Z. P. 1849, p. 120; 
Cat. An. p.9. Depressed, roundish, dull silvery white, margin with 
3 or 4 very large angular folds; porforation of lower valve small, 
firmly embracing the plug. 2%. Costa Rica. 
A. Rupis.—Pracuanomta R. Brod. Z. P. 1834.—Gray, 7%. P. 
1849; Cat. An. p. 10.—Popoprsmus Decrrrens, Phil. Wieg. 1837, 
teste Gray. Dirty white, thick, with irregular concentric wrinkles ; 
inside polished ; subcentral scars 2, rounded, separate, of nearly equal 
size, the hinder one rather more transverse: perforation moderate, 
fir oy embracing and enclosing the plug. 1%. Cuba. 
A. Macroscutsma. Desh. Poa Z. 18389; Mag. Zi. VBAL. AT: 
Mol. Ros. pt. 3, p.6; Sibir. Z. 242, t.19, f. 1 to 5.—Phil. N.C. 3 
p- 182, An. t. 1, f. 4.—Pracuanomia M. Gray, Cat. An. p. ilies 
Woodw. t. 16, f.4. Large, irregularly ovate, or suborbicular, inequi- 
valve, usually thick, greenish white, radiatingly (at times irregularly) 
ribbed; inner disk of the upper valve with a large dark green spot: 
subeentral scars 2, partly confluent on the lower hinder edge, the 
upper one the larger: lower valve often with a dark green margin, 
its perforation large, entire, a dull triangular excavation above it. 2. 
Kamtskatka. 
~ A, Foriata.—Pracuanomia F. Brod. Z. P. 1834.—Gray, Z. P. 
1849, p. 120; Cat. An. p.10. Subdiaphanous, subcircular, rough, 
subfoliaceous, dirty white, occasionally with very slight distant 
radiating ribs; inside of the upper valve splendent, purple-browu 
in the middle; subcentral scars 2, nearly united, the upper the 
larger and rather elongated, the lower small and rounded. JW Indies. 

«The A. Ivprrcata of Bruguiére (A. Muricara, D. p. 289, from 
Ch. 8, vig. at p. 65, f. C. D., copied EH. t. 171, f. 14, 5, and W. t. 11, 
Ff. 8) seems closely allied, if distinct. 
