INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 339 



species burrows like a mole, head-first, instead of backward. It can 

 also swim quite actively and is sometimes found swimming about in Hie 

 pools left on the flats at low-water. It is 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 still more 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," Eupagurus 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 III, 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 aiitennse, 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 it is 

 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 for a considerable time after 

 hatching, and were taken at the surface in the evening, in large num- 

 bers. The common prawn, Palwmonetes vulgaris, (Plate II, fig. 9,) 

 often occurs, associated with the Crangon, but it is 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 Eippa, 

 with which it agrees in habits, for it burrows in the sand like a mole. 



