318 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
beds were discovered in spots on which no scallops were previously known. In the same 
locality beds have apparently shifted in a single day; but such striking migrations 
are thought to be undertaken only by small bodies of scallops. 
6.— PARASITES OF THE SCALLOP. 
{a) Crabs . — Like tne oyster, the scallop is the host of a species of crab {Pinnotheres 
wacitZaittm) peculiar to it and to the common mussel {Mytilus eduUs). This parasite 
is lodged in the gill cavity of the mollusks and appears to exert no injurious effect on 
their life or growth. Mr. Eathbuu writes regarding it: 
It attains a larger size than the oyster-crah, and, as in the case of the latter, the females alone are 
parasitic, the males having only been found swimming at the surface of the sea. We have never heard 
of this species being eaten, probably because neither the mussel nor the smooth scallop has ever been 
much used as a food in this country. In the summer of 1880, while dredging off Newport, Rhode Island, 
the United States Fish Commission steamer Fish MawTc came upon extensive beds of the smooth scallop, 
from a bushel of which nearly a pint of these crabs were obtained. Again, in 1881, the same species 
was encountered in great abundance by the same party in Vineyard Sound, in Mytilus edulis. As au 
experiment, they were cooked along with the mussels and found to be very palatable, although their 
shell is, perhaps, somewhat harder than that of Pinnotheres ostremi.* 
Mr. F. W. Lunt, of West Tremont, Maine, informs the writer that four or five 
crabs are sometimes found lodged in a single scallop, and that even as many as ten 
have occasionally been observed. That the crab is not a constant inhabitant is well 
known, and some fishermen have never seen it. Mr. L. F. Gott, of Tremont, in pre- 
paring several hundred bushels of scallops for market, did not find a single crab. 
So far as can be learned, the crabs are never eaten on the Maine coast. 
(b) Boring-sponges.— The shells of many scallops, but more especially those of 
larger size, are more or less eaten by a boring-sponge {Gliona sulphurea), which attacks 
the shell and honeycombs it in all directions. The upper valve appears to be more 
frequently aifected. Ordinarily the sponge does not pierce the hard, glistening, inner 
lining of the shell, but confines its ravages to the softer outside layers. When the 
nacre is perforated, however, the irritation produced causes the scallop to throw over 
the opening a secretion of lime salts which quickly repairs the injury, and no harm 
results to the animal. The inner surfaces of some specimens are covered with small 
papillary elevations that are supposed to have been produced in this way. 
The fishermen, as a rule, do not think the sponge is responsible for the borings seen 
in the shells, but attribute them to a small worm that finds a shelter in the sponge. 
This worm is by some fishermen thought to be a real enemy of the scallop, and it is 
said that specimens of the mollusk are often found that have been bored through and 
killed by it. 
The truth of the matter seems to be that the chambers and channels seen in the 
scallop-shell are made by the boring-sponge, which may sometimes cause the death of 
the animal by irritation or otherwise. After reaching a certain age the sponge gen- 
erally dies, and the unoccupied recesses are then appropriated by a worm which is 
harmless so far as any power to bore through the shell is concerned. Mr. Eichard 
Eathbun, to whom 1 am indebted for the foregoing suggestion, informs me that there 
is no worm affecting the shellfish in our waters that is capable of puncturing a shell. 
The Fisheries and Fishery Industries of the United States. Section I, text, page 766. 
