PECTINIDA. 289 
margins straight, united by a narrow ligament; cartilage 
internal, in a central pit; adductor impression double, obscure ; 
pedal impression only in the left valve, or obsolete. 
Animal with the mantle quite open, its margins double, the 
inner pendent like a curtain, finely fringed ; at its base a row of 
conspicuous round black eyes (ocelli) surrounded by tentacular 
filaments; gills exceedingly delicate, crescent-shaped, quite dis- 
connected posteriorly, having separate excurrent canals; lips 
foliaceous ; palpi truncated, plain outside, striated within ; foot 
finger-like, grooved, byssiferous in the young. 
The scallop (P. maximus) and “ quin” (P. opercularis) are, m 
Europe, esteemed delicacies; the latter covers extensive banks, 
especially on the north and west of Ireland, in 15-25 fathoms 
water. The scallop ranges from 3-40 fathoms; its body is 
bright orange, or scarlet, the mantle fawn-color, marbled with 
brown; the shell is tsed for “scalloping” oysters; formerly it 
it was employed as a drinking cup, and celebrated as such in 
Ossian's ‘hall of shells.” An allied species has received the 
name of “St. James’s shell” (P. Jacobeus); it was worn by 
pilgrims to the Holy Land, and became the badge of several 
orders of knighthood. 
Most of the Pectens spin a byssus when young, and some, 
like P. varius, do so habitually; P. ntveus moors itself to the 
fronds of the tangle (Laminaria). 
The Rey. D. Landsborough observed the fry of P. opercularis, 
when less than the size of a sixpence, swimming in a pool of 
sea water left by the ebbing of the tide. ‘Their motion was 
rapid and zigzag; they seemed, by the sudden opening and 
closing of their valves, to have the power of darting like an 
arrow through the water. One jerk carried them some yards, 
and then by another sudden jerk they were off in a moment on 
a different tack.’”? European epicures regard the large species as 
dainty articles of food, and the American P. irradians, of late 
years, is increasingly sold in our markets. 
The shell of Pecten and the succeeding genera consists almost 
exclusively of membranous lamine, coarsely or finely corru- 
gated. It is composed of two very distinct layers, differing in 
color (and also in texture and destructibility), but having 
essentially the same structure. Traces of cellularity are some- 
times discoverable on the external surface; P. nobilis has a 
distinct prismatic-cellular layer externally.— CARPENTER. 
PALLIUM, Schum., 1817. (Dentipecten, Ruppell, 1835. Decado- 
pecten, Sowb., 1839) Hinge obscurely toothed. P. plica, 
fuinn, (exxxni, 15). 
CHLAMYS, Bolten, 1798. (Argus, Argoderma, Poli.) Shell 
subequivalve, with radiating striz or ribs. JP. tslandicus, 
Chemn, (cxxxiii, 16), 
