314 TESTACEOUS MOLLUSCA. 
smooth. Inside of upper valve with a defined white spatula some- 
what in the shape of an isosceles triangle, with an excurved base 
radiating from the light green ligament and enclosing the 3 scars; 
plug-scar rounded subquadrate, not much larger than the other 
2 round ones. 2. California; Mexico. The scars vary as to rela- 
tive position. 
AS Mryros) “Gray, Z. P1840, pAb; ion Eyal Cat An 
p-21. More or less orbicular; upper valve white or yellowish (espe- 
cially at the umbones), most closely rayed with elevated strie; apex 
marginal; subcentral scars 3, the 2 upper small, subcentral, one 
above the other, the lower one large, nearly circular, almost in the 
middle of the shell. Lower valve white or pale green, the perforation 
rather small. 2. Australia. 
A. Apamas. Gray, Z. P. 1849; p.117; Cat. An. p.18. Red, 
thick, with numerous distinct radiating ribs, most indistinct on the 
edge of the lamina; within pearly red, with small white disk. Upper 
subcentral scar oblong, arched below ; lower scars subequal, separate, 
yet close together, and nearly on the same line. Galapagos. 
A. AcHmus. Gray, Z. P. 1849, p. 116; Mol. t. 4, f. 2; Cat. An. 
p- 16.—Woodw. t. 16, f. 3. Purplish, smooth; upper valve generally 
convex, its umbo rather acute; inside purplish white; upper of the 
3 subcentral scars large, its lower edge slightly arched, the 2 lower 
scars small, nearly equal-sized: perforation large. Hindostan. 
A. Axxrctus. Gray, Z. P.1849, p.117; Cat. An. p.19. Irregular ; 
upper valve convex, reddish, pearly within, upper subcentral scar 
large, oblong, 2 lower scars nearly as large (especially the lowest of 
the 3), close together, yet not confluent. Peru. 
«i Upper valve with only 2 subcentral nuseular scars., 
(PLACUANOMIA.) 
A. Pareiirormis.* Lin. (not Ch.) 1151.—Brit. Mol. 2, p. 334, 
pl. 56, f. 5, 6— OstrEum Srriatum, Da Cos. t. 11, f. 4—A. Unpv- 
Latim, &e., Ch. 699.—A. Unputata, Gm.—Mont. 157, t. 4, f. 6.— 
Turt. B. p. 230, t. 18, f. 8, 9, 10.—Ostrea 8. Pult.——Don. t. 45.— 
Pracuanomia P, Gray, Cat. An. p. 12. Suborbicular; upper valve 
with about 20 to 30 slightly flexuous radiating ribs, their intervals 

t See, too, the A. AMaBa&uUS, Cyrmum, Dryas, BELEsts, ACONTEs, 
Fipenas, Pacitus, Larpas and Hamituus, of Gray (Z. P. 1849, and 
Cat. Ano.); also the A. Cutnensts of Philippi (Zeit. Mal. 1848, and 
N. C. 8, An. t. 1, f. 1), whose figure might be taken for Epnippium. 
Compare, likewise, the A. Austranis of Gray (Apa. Fly, p. 362), and 
the A. Simpiex of D’Orbigny. 
