436 MARINE INVERTEBRATES 
of a well-known Mediterranean pecten (P. jacobius), found com- 
monly in Palestine, became an emblem of religious significance 
during the middle ages. Returning crusaders fastened to their 
garments a specimen of “St. James’s shell” as an evidence of the 
fact that they had been to the Holy Land, and the design of the 
shell came to be adopted upon many coats of arms and also in the 
insignia of various orders of devout and adventurous knights of 
the middle ages. 
The animal is of the highest type of monomyarian mollusks, 
that is, of bivalve mollusks with only a single adductor muscle. 
Unlike most pelecypods, which have a very small foot, Pecten 
rarely has a byssus, and is neither a stationary nor a sluggish crea- 
ture. It can propel itself through the water by spasmodically clos- 
ing and opening its valves, in an eccentric, darting sort of flight, 
though most of the time it rests quietly upon the bottom. The 
mantle is entirely open and highly ornate about its margin, 
which is, furthermore, the seat of many eyes, capable, appa- 
rently, of no mean degree of vision. The adductor muscle is very 
large and strong, and occupies a central position, about which the 
gills circle; the latter are plainly filamentous. 
P. magellanicus. The largest of the east-coast species of Pecten. 
It is a Northern species, and was long known by the name of P. tenu- 
éscostatus — a name given to it on account of its very numerous radiat- 
ing striz; but it was later discovered that the North Atlantic form was 
in reality the same asthe P. magellanicus of Patagonia. The latter being 
the older name and entitled to priority, our shell became P. magellanicus, 
the other name falling within its synonymy. The length and height of 
this scallop are from five to five and a half inches. One valve is more 
convex and slightly larger than the other, the smaller being lighter in 
color. The valves gape considerably along their upper margin below 
the hinge. The cartilage-pit is deep. North of Cape Ann this large 
species 1s of common occurrence in moderately deep water. The deeper 
bays and arms of the sea which everywhere penetrate the Maine coast 
are its favorite resorts. A good way to catch pectens is to lower a fishing- 
line at a spot where the fishermen report “ scallop-ground,” and drag it 
along over the bottom, Sooner or later it will enter the open shell of 
some pecten, which will instantly close its valves upon the string and 
allow itself to be drawn out of the water. In Maine these large scallops 
are eaten, but they have not found great favor in the city markets. In 
color they vary from reddish through brown to ashen. 
P. islandicus. A species not so large as the last, with more promi- 
nently raised ribs (about fifty to one hundred in number), which are cov- 
