314 TESTACEOUS MOTXUSCA. 



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 jiosition. 



A. Elykos. Gray, Z. P. 1849,;;. 118, Mol. t. 4,/. 1 ; Cat. An. 

 ^9. 21. More or less orbicular; upper valve white or yellowish (espe- 

 cially at the umbones), most closely rayed with elevated strise ; 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. Adamas. 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, Acieeus. Gray, Z. P. 1849, p. 116 ; Mol. t. 4,/. 2 ; Cat. An. 

 p. 16. — Woodw. t. 16,/. 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. Alectus. Gray, Z. P. 1849, ^.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. l 



** Upper valve ivith only 2 subcentral muscular scars. 

 (Placuanomia.) 



A. Patelliformis.* Lin. (not Ch.) 1151. — Brit. Mol. 2, p. 334, 

 pi. 56,/. 5, 6. — Ostreum Striatum, Da Cos. t. 11, /. 4. — A. Undu- 

 latim, &c, Ch. 699. — A. Undulata, Gm. — Mont. 157, t. 4, /. 6.— 

 Turt. P.p. 230, t. 18,/. 8, 9, 10.— Ostrea S. Pult.—Don. t. 45.— 

 Placuanomia P. Gray, Cat. An. p. 12. Suborbicular ; upper valve 

 with about 20 to 30 slightly flexuous radiating ribs, their intervals 



1 See, too, the A. Amab^eus, Cyt/Eum, Dryas, Belesis, Acontes, 

 Fidenas, Pacilus, Larbas and Hamillus, of Gray (Z. P. 1849, and 

 Cat. Ano.) ; also the A. Chinensis of Philippi (Zeit. Mai. 1848, and 

 .V. C. 3, An. t. 1,/. 1), whose figure might be taken for Ephippium. 

 Compare, likewise, the A. Australis of Gray (Apx. Fly, p. 362), and 

 the A. Simplex of D'Orbigny. 



