INVERTEBEATE ANIMALS OF VINEYARD SOUND, ETC. 363 



the North. Pacific coast ; 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 Brunswick 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, Astenas 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," Ojphiura. 

 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-quarter 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 in its 

 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 Obelia 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 XXXVIII, 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 

 sometimes be-recognized by small cracks radiating from the hole when 

 the tide leaves them uncovered. 



The Sagartia modesia (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 XXXVIII, 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 Port Macon, where it is 

 often thrown up by storms, and it has also been found at Great Egg Har- 



