[363] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 69 
the North Pacific eoast ; and in depth it ranges from low-water mark to 
430 fathoms, off Saint George’s Bank, where it was dredged by Messrs. 
Smith and Harger. When living its color is usually a rich purplish 
brown, but it soon turns green when taken from the water. It gives a 
dark green or blackish color to alcohol, which stains very injuriously 
any other specimens put in with it. The fishermen on the coast of 
Maine and New Bruiswick sometimes prepare an indelible marking-ink 
from these “sand-dollars,” by rubbing off the spines and skin and, 
after pulverizing, making the mass into a thin paste with water. <A 
number of fishes have been found to swallow this unpromising creature 
for food, and the flounders consume large numbers of them. 
The common green star-fish, Asterias arenicola, (p. 326, Plate XXXV, 
fig. 269,) is sometimes met with on sandy shores, but is much less abun- 
dant than on rocky shores. The curious “ brittle star-fish,” Ophiura 
olivacea, is sometimes found among the eel-grass on sandy shores, espe- 
cially in tide-pools, in sheltered localities. It may be recognized by its 
nearly circular, disk-like body, about three-quarters of an inch in diameter, 
with five round, rather slender, tapering, stiff-looking arms, about three 
inches long. The color is bright green, much like that of the eel-grass 
among which it lives. When at home in the water it moves about over 
the sand quite rapidly by means of its arms. When taken from the 
water it does not usually break itself up into numerous fragments, 
as readily as most of its related species do. It is rather southern inits 
distribution, and Vineyard Sound is perhaps its northern limit. It 
extends southward at least to North Carolina. 
Of acalephs there are no species known to me that properly belong 
to the sandy shores, but Hydractinia polyclina (p. 328) is often found 
on the shells carried about by the hermit-crabs, in such situations, and 
there are species of QObelia and other hydroids that sometimes grow on 
the eel-grass in the tide-pools, but they are much more frequent in other 
situations. 
Among the Polyps we find several species proper to sandy shores and 
specially adapted to this mode of life. One of the most interesting of 
these is the Halocampa producta, (p. 330, Plate X XXVIII, fig. 285,) 
which has already been described. This often occurs in the sand at 
low-water mark, and makes round holes about a foot deep, which can 
sometimés be recognized by small cracks radiating from the hole when 
the tide leaves them uncovered. 
The Sagartia modesta (p. 330) is also found buried in the sand at low- 
water, especially where there is also some gravel with the sand. The 
Sagartia leucolena (p. 329, Plate XX XVIII, fig. 284) is sometimes found 
in similar situations, but belongs properly to the rocky shores. 
The Paractis rapiformis is a species that is still little known. It lives 
buried deeply in the sand at and below low-water mark. It appears to 
be common on the coast of North Carolina, at Fort Macon, where it is 
often thrown up by storms, and it has also been found at Great Egg Har- 
