[339] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 45 
species burrows like a mole, head-first, instead of backward. It can 
also swim quite actively and is sometimes found swimming about in the 
pools left on the flats at low-water. Itis occasionally dug out of the sand 
at low-water mark, and is often thrown up by the waves, on sand- 
beaches, but it seems to live in shallow water on sandy bottoms in 
great numbers, for in seining on one of the sand-beaches near Wood’s 
Hole for small fishes, a large quantity of this species was taken. Its 
color is yellowish white, tinged with purple on the back. It is one of 
the favorite articles of food of many fishes. Mr. Smith found the 
young abundant at Fire Island, near high-water, burrowing in the sand. 
This species is stillmore abundant farther south. 
The curious long-legged “ spider-crab,” Libinia canaliculata, is fre- 
quently met with at or just below low-water mark on sandy shores, but 
its proper home is on muddy bottoms. 
Creeping, or rapidly running, over the bottom in shallow water, or in 
the tide-pools on the flats, the smaller ‘‘ hermit-crab,” Hupagurus longi- 
carpus, (p.313,) may almost always be observed ensconced in some dead 
univalve shell, most commonly that of Ilyanassa obsoleta. This species 
is still more abundant among eel-grass, and on muddy shores. 
The common ‘“sand-shrimp,” Crangon vulgaris, (Plate ILI, fig. 10,) 
always occurs in great numbers on the sandy flats and in the tide-pools 
and rivulets, as well as on the sandy bottoms in deeper water off shore. 
This species is more or less specked irregularly with gray, and imi- 
tates the color of the sand very closely. When resting quietly on the 
bottom, or when it buries itself partially and sometimes almost entirely, 
except the eyes and long slender antenne, it cannot easily be distin- 
guished by its enemies, and, therefore, gains great protection by its 
colors. When left by the tide it buries itself to a considerable depth in 
moist sand. It needs all its powers of concealment, however, for itis 
eagerly hunted and captured by nearly all the larger fishes which fre- 
quent the same waters, and it constitutes the principal food of many of 
them, such as the weak-fish, king-fish, white perch, blue-fish, flounders, 
striped bass, &c. Fortunately it is a very prolific species and is abun- 
dant along the entire coast, from North Carolina to Labrador, wherever 
sandy shores occur. The young swim free fora considerable time after 
hatching, and were taken at the surface in the evening, in large num- 
bers. The common prawn, Palemonetes vulgaris, (Plate Il, fig. 9,) 
often occurs, associated with the Crangon, but itis much more abundant 
among the eel-grass, and especially in the estuaries where it has its 
proper home. As this is one of the most abundant species and of 
great importance as an article of fish-food, it will be mentioned again, 
with more details, in connection with the fauna of the estuaries. 
Several species of smaller crustacea also burrow in the sand at low- 
water mark. One of the most remarkable of these is an Amphipod, the 
Lepidactylis dytiscus, which by its external form reminds one of Hippa, 
with which it agrees in habits, for it burrows in the sand like a mole. 
