[463] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 169 
cies is yellowish brownin color. The larva of a fly belonging to the Mus- 
cide, and growing to the length of three-quarters of an inch, occurs 
beneath the sand at low-water mark, and was also dredged off-shore in 
three or four fathoms of water. 
In the shallow waters and on the flats the common shrimp, Crangon 
vulgaris, (p. 339, Plate IIT, fig. 10,) is always to be found in abundance 
where the water is not too much freshened by the rivers. The prawn, 
Palemonetes vulgaris, (p.339, Plate IT, fig. 9,) is also frequent on the sandy 
bottoms, though more abundant among the eel-grass, and this species 
extends far up the estuaries into the mouths of rivers, where the water 
is but little salt. 
The most abundant Annelids are Nereis virens, (Plate XI, figs. 47-50,) 
N. limbata, (Plate XI, fig. 51,) Rhynchobolus dibranchiatus, (Plate X, figs 
43, 44,) R. Americanus, (Plate X, figs. 45, 46,) and Scolecolepis viridis V., 
(p- 345,) all of which burrow in the sand at low-water mark in the same 
way as on the shores of the sounds. 
Under vegetable débris and stones, at high-water mark, the Halo- 
drillus littoralis (p. 324) and Olitellio trroratus (p. 324) occur in abun- 
dance. The Lumbriculus tenwis burrows among the roots of grass at 
high-water mark. 
The most abundant Gastropod shells are Jlyanassa obsoleta, (Plate 
XXI, fig. 13,) Tritia trivittata, (Plate X XI, fig. 112,) Bittium nigrum, 
(Plate XXIV, fig. 154,) Astyris lunata, (Plate XXT, fig. 110,) which oceur 
on the flats and on the bottom in shallow water, but all are more com- 
mon among eel-grass. The Melampus bidentatus (Plate XXYV, figs. 169, 
169a) is very abundant among the grass and weeds at and just above 
high-water mark. It contributes largely to the food of the minnows 
and other small fishes, as well as to that of many aquatic birds. The 
Crepidula convexa (Plate XXIII, fig. 128) is frequent on the dead shells 
occupied by the small hermit-crab, Hupagurus longicarpus, (p. 313,) 
which is abundant, running over the bottom in shallow water. 
The most abundant bivalves are the long clam, Mya arenaria, (Plate 
XXVI, fig.179,) and Macoma fusca, (Plate XXX, fig. 222.) These both 
occur burrowing in the sand between tides, and both occur far up the 
estuaries, where the water is very brackish, but they are most abun- 
dant where there is a mixture of sand and mud. In the-estuaries the 
long clam is extremely abundant all along the coast from’ New Jersey 
to the Arctic Ocean, as well as on all the northern coasts of Europe 
It also occurs south of Cape Hatteras, as at Beaufort, North Carolina, 
but in greatly diminished numbers. North of New York it is very ex- 
tensively used as an article of food. North of Cape Cod it is the com- 
mon “clam” of the fishermen; and north of Boston it almost entirely 
displaces, in the markets, the “round-clam,” or “quahog,” Venus mer- 
cenaria, which is the common clam at New York and farther south. 
Along the southern coast of New England both species are abundant, 
and both are sold in large quantities in the markets. South of New 
