162 TESTACEOUS MOLLUSCA. 
PECTUNCULUS. 
Orbicular, doubly convex, equivalve, subequilateral, and close ; 
hinge arcuated, teeth numerous, oblique, serrated, alternately 
inserted into the opposite valves, middle ones obsolete ; ligament 
external. 
* Surface not ribbed. 
. Pirosus.* Lam. 2.—Philip. p. 61.—Arca P. Lin.—W. 
t.9. f. 37.—P. Grycimeris. Unpatus J’ Pirnosus. Turton. Biv. 
t.12. f. 1, 2,3,4.—P. Marmoratus. Lam.4.—Arca P. D.p. 
242.—W. t. 9. f. 36.—Anca M. Gimel. 3314.—Ch. f. 560. 5 
563.—List. t. 247. f. 82.—Knorr. 6. t.14. f. 4.—Gualt. t. 72. 
G.—E. t. 310. f. 3. Orbicular-ovate, becoming inequilateral by 
age, white with angular red streaks arranged either longitudinally 
or transversely (sometimes flesh colour with white spots and an- 
gular red ones) minutely decussated, the apices obliquely incurved, 
approximate : inside white or whitish : epidermis velvety. 12.— 
Atlantic and Mediterranean. 
P. Sicutus. Reeve. Ic. f.41.—P. Grycimeris. am. 1.— 
Philip. p. 60.—P. Pitosus. Sow. G'.— Reeve. Sys. t. 83. f. 1.— 
Ch. f. 564.—Poli. t. 25. f.17, 8 ?—List. t. 247. f. 82? Orbicular, 
rather broader than long, all but equilateral, rather depressed 
(except when aged) uniform, brownish red (usually with darker 
zones and the beaks often tipped with white) radiated by 
minute strie and delicate pale rather distant lines having the 
appearance of obsolete sulci : epidermis silky, brown. 3.—Medi- 
terranean. 
P. Unputatus. Lam. 3.—Del. t. 12. f. 1.—Arca Unpata ? 
Tin.— Brug. Dic.p. 114%  Ovate orbicular, tumid, inequilateral, 
anteriorly angulated and the longitudinal furrows very apparent : 
white with small waved rufous spots disposed in transverse rows : 
beaks with a straight inclination to each other. 13.—America? 
P. Scriprus. Lam. 5.—Reeve, Ic. f.6 “%—Arca Scripta. 
D. p. 243.—Born. t. 6. f. 1. a.—List. t. 246. f. 80.—E. t. 311. 
f. 8.—W.t.9. f. 39.  Orbicular, rather depressed, with minute de- 
cussated strize, whitish with angular fulvous lines ; beaks slightly 
curved anteriorly : within white stained with yellow at the anterior 
end, crenations of the margin about fifty and only visible in the 
centre. 14.—St. Domingo. 

1 From an examination of Linneus’s own specimen, I can 
safely assert that M. Deshayes is in error in considering this shell 
to be the Gilycimeris of Linneus. The specimens of the latter 
are the Violascens of Lamarck. 
