31b 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
also adorned with a row of conspicuous round black eyes around its base. The lungs or gills are 
between the two folds of the mantle, composed of fibers pointing outward, of delicate form and free 
at their outer edges, so as to float loosely in the water. The mouth is placed between the two inmost 
gills, where they unite. It is a simple orifice, destitute of teeth, but with four membranous lips on each 
side of the aperture. The mechanism by which respiration and nutrition are secured is elaborate and 
exceedingly interesting. The filaments of the gill fringe, when examined under a powerful micro- 
scope, are seen to be covered with numberless minute, hair-like processes, endowed with the power of 
rapid motion. These are called cilia, and when the animal is alive and in situ, with the valves gaping, 
may be seen in constant vibration iu the water, generating by their mutual action a system of cur- 
rents by which the surface of the gills is laved, diverting toward the mouth animalcules and other 
small nutritious particles.* 
The shell of the scallop has been described as “ orbicular, rather higher than long, 
thin and translucent when young, thick, strong, and opaque when mature, equilateral, 
inequivalve, the lower valve being nearly flat and not attaining the edge of the upper 
valve by an eighth of an inch or more ; upper valve moderately convex, valves widely 
gaping near the hinge, surface everywhere sculptured with radiating j)unctured lines 
or grooves about half as wide as the spaces between them, somewhat zigzag in their 
course. These lines are crossed by closely arranged lines of growth, which on the 
convex valve are scalloped or vaulted 6ver the radiating lines ; flattened valve white, j 
convex valve dingy, reddish-brown, or flesh-colored. Hinge margin narrow, straight, 
ears equal, the notch in the lower valve rounded and shallow. Interior white, smooth, 
glossy, with minute radiating lines not corresponding to the exterior grooves.” t 
5.— SIZE, GROWTH AND DEATH, HABITS, ETC. 
The scallop shares with other deep water mollusca the obscurity concerning their 
life history which is thrown around them by the great difficulties iu the way of a com- 
prehensive research. The commercial fisherman, as a rule, is not a close observer of 
inconspicuous vital jihenomena, and he can not be expected to depart beyond a certain 
point from the realms of practical business to delve in the domain of natural science. 
In the case of the particular species under consideration, the writer found that what 
would in almost any other sphere have been an exhaustive inquiry was almost barren 
of results. Until the establishment of large marine aquaria, iu which the lives of 
fish, crustaceans, mollusks, and other orders can be studied with but little or no 
departure from the natural conditions, it would appear that a complete knowledge of 
the habits and of the most practical methods of propagation, cultivation, and pro- 
tection of many of our important water animals will always be lacking. 
Viewed from the standpoint of size alone, the giant scallop is probably the largest 
edible mollusk on the Atlantic coast of the United States. The average diameter of 
the specimens taken for market on the coast of Maine is about 5^ inches, although much 
larger individuals are not uncopamon, and those the size of a nickel coin are sometimes 
brought up. The largest examples recorded from Mount Desert, Castine, and Little 
Deer Isle have been 9 inches in diameter. The edible muscular portion of a scallop of 
this size is about 3 inches in diameter and weighs 9 or 10 ounces. The average size 
of the “ meat,” however, is a little more than 1 inch in diameter. 
The general impression among fishermen is that the scallop is a rapid grower, reach- 
ing maturity in a few years. In this respect the giant scallop agrees with the prob- 
* Overland Monthly, April, 1873. 
tGould, Invertebrates of Massachusetts, 1870, pp. 19C, 197. 
