TRIBE ARCACEA. 163 
P. Pennaceus. Lam. 6.—Reeve Ic. f. 24. (good)— Knorr. 
5. t. 30. f. 3.—Arca Decussara. Lin. 1142?—D. p. 239? 
—W.t. 9. f. 31. Orbicular, swollen, decussately striated, longi- 
tudinal striz 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. Rusens. Lam. 7.—. t. 310. f. 3.—Reeve. Ic. f. 23? 
Orbicular, convex, decussated by very delicate strize, pale reddish 
with many zones and numerous small darker spots: ligamental 
area narrow: one large internal brown stain. 23?.—M. Deshayes 
states that the figure quoted by Lamarck represents Gilycimeris. 
P. Aneutatus. Lam. 8.—Reeve. Ic. f. 30.—Arca A. 
Gmel.—_D. p. 240?7—W. t. 9. f. 34.—Ch. f. 567.—List. 
t. 245. f. 76?—Brug. no. 28. Subcordate, ventricose anteriorly 
angulated, longitudinally sulcated and striated rich chesnut (some- 
times with white splotches): ligamental area rather short. 14.— 
America. 
P. Srerzuatus. Lam. 9.— Reeve. Ic. f. 5.—Arca 8. 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 strie. 2.—Portugal. 
P. Patutens. Lam. 10.—Arca P. Lin. 1142.—D. p. 246. 
—W. t. 9. f. 33. Lenticular, inequilateral, with decussated striz. 
of which the longitudinal are the more prominent, white clouded 
or spotted with very pale violet; beaks approximated and not in- 
clining. 13.—Indian Ocean.—Variety. With more colour, 
beaks not so approximated and rather oblique.— Gulf of Taren- 
tum. ‘* Probably only a young Violascens.” Drsu. 
P. Grycimeris. (not Lam.) Arca G. of Linnzeus (fide his 
own specimens.) P. Vionascens. Lam. 11.—Payr. t. 2. f. 1. 
—Reeve. Ic. f.9.—Del. 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. 13..2.—Mediterranean.—Young. P. 
Nummarius. Lam. 14.—Arca N. Lin. (certo.)—D. p. 243. 
Densely variegated with liver colour on a white ground, with 
prominent concentric striee.! 

1 Mr. Reeve assures me (having examined Lamarck’s own 
specimen,) that the Zonalis is but a variety of this species. 
M .2 
