CONCHIFEIIA. 257 



sion double, obscure ; pedal impression only in the left valve, or obsolete 

 (fig. 173). 



Animal with the mantle quite open, its margins double, the inner pen- 

 dent like a curtain {m) finely fringed; 

 at its base a row of conspicuous round 

 black eyes {ocelli) surrounded by 

 tentacular filaments; gills {fir) ex- 

 ceedingly delicate, crescent-shaped, 

 quite disconnected posteriorly having 

 separate excurrent canals ; lips foli- 

 aceous ; palpi truncated, plain out- 

 side, striated within ; foot finger-like, 

 grooved, byssiferous in the young. fig. 179. Pecten varius.* 



The Scallop (P. maximits) and " quin" (P. oi^ercular'bs) are esteemed 

 delicacies ; the latter covers extensive banks, especially on the N. and W. of 

 Ireland, in 15 to 25 fm. water. The scallop ranges from 3 — 40 fms. : its 

 body is bright orange, or scarlet, the mantle fawn-colour, marbled with 

 brown ; the shell is used for " scalloping" oysters, formerly 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. Jacohozus) ; 

 it was worn by pilgrims to the Holy-land, and became the badge of several 

 orders of knighthood.f 



Most of the Pectens spin a byssus when young, and some, like P. varius, 

 do so habitually ; P. niveus moors itself to the fronds of the tangle {La- 

 minaria.) 



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 zig-zag ; 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." 



The shell of Pecten and the succeeding genera consists, almost exclusively 

 of membranous laminae, coarsely or finely corrugated. It is composed of 

 two very distinct layers, differing in colour (and also in texture and destruc- 

 tibility), but having essentially the same structure. Traces of cellularity 

 are sometimes discoverable on the external surface ; P. nobilis has a distinct 

 prismatic -cellular layer externally. {Carpenter.) 



* The Pectens do not open so wide as here represented ; their " curtains" remain 

 in contact at one point on the posterior side, separating the branchial from the ex- 

 halent currents. 



t When the monks of the ninth century converted the fisherman of Gennesarat 

 into a Spanish warrior, they aosigned him the scallop-shell for his "cognizance." — 

 Moule's Heraldry of Fish. 



N 2 



