TRIBE ARCACEA. I 63 



P. Pennaceus. Lam. 6. — Reeve Ic. f. 24. {good) —Know, 

 5. t. 30. /. 3.— Arca Decussata. Xm! 1 142 ?* — B. p. 239? 

 — IF. t. 9. y. 31. Orbicular, swollen, decussately striated, longi- 

 tudinal stria? the stronger, whitish irregularly painted with large and 

 small dark brown spots : umbones bent inwards to the posterior 

 end of the ligament : lunule heart-shaped, with transverse red rays. 

 2. — West Indies. 



P. Rubens. Lam. 7—E. t. 310. /. 3.— -Reeve. Ic. f. 23 ? 

 Orbicular, convex, decussated by very delicate striae, pale reddish 

 with many zones and numerous small darker spots : ligamental 

 area narrow : one large internal brown stain. 2|. — M. Deshayes 

 states that the figure quoted, by Lamarck represents Glycimeris. 



P. Angulatus. Lam. 8. — Reeve. Ic. f. 30.— Arca A. 

 Gmel.—B. p. 240? — W. t. 9. /. 34.— Ch. f. 567.— List, 

 t. 245. f. 761 — Brug.no. 28. Subcordate, ventricose anteriorly 

 angulated, longitudinally sulcated and striated rich chesnut (some- 

 times with white splotches): ligamental area rather short. If. — 

 America. 



P. Stellatus. Lam. 9. — Reeve. Ic. f. 5. — Arca S. Brug. 

 no. 32. — D. p. 242. — Bon. t. 2. f. 62. Orbicular-heart-shaped, 

 yellowish violet, umbones peculiarly starred with white, ornamented 

 with very faint rather remote longitudinal strise. 2. — Portugal. 



P. Pallens. Lam. 10.— Arca P. Lin. 1142.— D. p. 246. 

 — W. t. 9.f. 33. Lenticular, inequilateral, with decussated striae, 

 of which the longitudinal are the more prominent, white clouded 

 or spotted with very pale violet ; beaks approximated and not in- 

 clining. 1^. — Indian Ocean. — Variety. With more colour, 

 beaks not so approximated and rather oblique. — Gulf of Taren- 

 tum. " Probably only a young Violascens." Desh. 



P. Glycimeris. (not Lam.) Arca G. of Linnaeus (fide his 

 own specimens.) P. Violascens. Lam. 11. — Payr. t. 2. f. 1. 

 — Reeve. Ic. f. 9. — Bel. t. 12. f. 2. Heart-shaped orbicular 

 oblique (becoming tumid by age,) greyish or reddish violet with paler 

 radiating lines having the appearance of sulci or obsolete ribs, and 

 concentrically striated on the umbones : beaks directly incurved 

 and situated nearly in the centre of the ligamental area : anterior 

 side elongated and angulated by age : within, more or less stained 

 with brown anteriorly. If.. 2. — Mediterranean. — Young. P. 

 Nummarius. Lam. 14. — Arca N. Lin. (certo.) — B. p. 243. 

 Densely variegated with liver colour on a white ground, with 

 prominent concentric striae. 1 



1 Mr. Reeve assures me (having examined Lamarck's own 

 specimen,) that the Zonalis is but a variety of this species. 



m 2 



