PECTINID^. 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 margius 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, in 

 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 used 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. Jacobseus) ; 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 habituall}'^ ; P. niveus moors itself to the 

 fronds of the tangle (Laminaria). 



The Rev. 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; the}^ 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 laminae, coarsely or finel}'' 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. nohilis has a 

 distinct prismatic-cellular layer externally. — Carpenter. 



PALLIUM, Schum., 1817. (Dentipecten, Ruppell, 1835. Decado- 

 pecten, Sowb., 1839 ) Hinge obscurely toothed. P. plica, 

 Linn, (cxxxiii, 15). 



CHLAMYS, Bolten, 1798. (Argus, Argoderma, Poll.) Shell 

 subequivalve, with radiating striae or ribs. P. islandicus, 

 Chemn. (cxxxiii, 16). 



