TRIBE ARCACEA. 165 



Arca EauiLATERA. Gmel.~D. p. 240.— Ch. f. 562. — E. f. 

 11. /. 2. — W. t. 9. /. 32. Orbicular, subequilateral, chesnut, 

 mottled with white, with numerous longitudinally striated ribs, 

 which become obsolete towards the beaks which are not inclined ; 

 within white. 1-|. — W. Indies. 



P. Pectiniformis. Lam. 16. — Reeve. Ic. f. 11. — Arca 

 Pectunculus. Li7i. \\A2.—D. p. 238. — IF. t. 9. f. 29.— Ch. 

 f. 568. — E. t. 311. y. 5. Suborbicular, thick, moderately convex, 

 somewhat eared, whitish more or less tinged with flesh colour, and 

 marked with brown wavy riband-like stripes, or spots, the ribs 

 and interstices both broad and the surface roughened by fine raised 

 transverse wrinkles ; beaks small and not inclining : within white 

 stained with chesnut at the hinge and near the beaks, the margin 

 plaited. \\. — Asiatic and American Seas. A sHght incurvation 

 of the anterior margiii. 



P. Pectinatus. Lam. 17. — Reeve. Ic. f. 28, — Arca P. 

 Gmel. 3313.— i>. p. 239.— Ch.f. 570, 1.—^. ^.311./. 6.— 

 JV. t. 9. f. 30. Lenticular, rather depressed, whitish with wavy 

 brown transverse markings or small spots, and numerous smooth 

 rather flattened ribs and narrow interstices : white within and the 

 margin crenated. f. — W. Indies. — Variety from Brazil. White 

 with rufous spots. 



J*. Radians. Lam.\8. Suborbicular, transverse, inequilateral, 

 rufous the umbones very white, with very numerous fine, 

 longitudinally striated ribs. — Variety. With the ribs broader. 

 1^. — Nov Holland. 



P. ViTREus. Lam. 19. Orbicular depressed, somewhat earedl, 

 thin, pellucid, with transversely striated almost granular longitu- 

 dinal ribs, white with a few orange dots ; beaks small and acute : 

 the hinge formed of two straight lines which almost form a right 

 angle at the beaks and are each furnished with from twelve to 

 fifteen oblique teeth. 1|-. — South Seas. 



P. MxjLTicosTATus. Sow. Z. P. \S32.—Reeve. Ic. f. 26. 

 Suborbicnlar, white mottled with chesnut, rust-colour, and ashy- 

 grey; with numerous radiating small rounded ribs which are 

 transversely striated : umbones posteriorly inflected. \\. — South 

 America. 



P. Parcipictus. Reeve. Z. P. 1843. — Reeve. Ic. f. 14, 

 Kather obliquely heart-shaped, radiately ribbed ; ribs flat, often 

 grooved up the middle, interstices deep ; white sparingly variegated 

 with yellowish chesnut undulated zones and patches : interior 

 white with a purple posterior stain. 1. — " The ribs are peculiarly 

 firm and squarely grooved out." 



P. AuRiFLTJUs. Reeve. Z. P. 1843. — Reeve. Ic. f. 17. 

 Orbicularly heart-shaped, inequilateral radiately ribbed, ribs broad 



