[427] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 133 
bases. Where eel-grass or algze afford opportunities for its attachment, 
the M. Manhattensis (p. 311, Plate XX XIII, fig. 250) generally occurs. 
The Bryozoa are not numerous, unless where dead shells are scattered 
over the sand for their attachment, when many of the same species that 
inhabit shelly bottoms may oceur, The only species that are frequent 
on the true sandy bottoms are Bugula turrita, (Plate XXXIV, figs. 258, 
259,) which occurs attached to eel-grass, &c., and Hscharella variabilis, 
(p. 311, Plate XX XIII, fig. 256,) which inerusts dead shells or other solid 
objects; with the last, Membranipora lineata, (p. 406,) and several other 
species may sometimes be found. 
Several species of Echinoderms inhabit the sandy bottoms. The most 
abundant one is the “sand-dollar,” Hehinarachnius parma, (p. 362, Plate 
XXXV, fig. 267,) which occurs in immense numbers on nearly all sandy 
bottoms, except on the most exposed shoals. Another related species, 
Melitta testudinaria, was dredged two or three times in Vineyard Sound, 
but the specimens were dead and broken. It is a very abundant species 
south of Cape Hatteras, and may be distinguished by having five large 
oblong perforations near the edge. 
At least three species of Holothurians live upon the sandy bottoms. 
The most common one is the Thyone Briareus, (p. 362,) conspicuous on 
account of its large size and dark purplish-brown color, as well as for the 
numerous long papille that cover its body. It was found on a sandy bot- 
tom off Waquoit, with the Hulima oleacea (Plate XXIV, fig. 149) adher- 
ing to its surface, just as they occurred together on shelly bottoms, (see p. 
418.) The Pentamera pulchella, (p. 420,) also inhabits sandy bottoms, in 
shallow water. During the past winter Mr. Vinal N. Edwards collected 
numerous specimens of this and the preceding species on Nobsca beach, 
after storms. They doubtless live in the sand, in shallow water, a short 
distance off the beach. In similar situations the Caudina arenata, (p. 362, 
occasionally occurs, but itis apparently rare in this region. It has athick, 
yellowish white, harsh skin, without suckers, and its body tapers off into 
a slender caudal portion. The common star-fish, Asterias arenicola, 
(p. 326, Plate XX XV, fig. 269,) isnot uncommon on sandy bottoms, though 
more abundant in rocky and shelly localities. The Ophiura olivacea 
(p. 363) lives among the patches of eel-grass in shallow water on the 
sandy bottoms, and travels over the surface of the sand quite rapidly 
by means of its slender, flexible rays. 
Of Hydroids very few species ordinarily inhabit sandy bottoms, and 
the only one that is usually met with is Hydractinia polyclina, (p. 328,) 
which lives on the shells occupied by hermit-crabs. Others occasionally 
grow on the eel-grass or on dead shells. 
The Cliona sulphurea, (p. 421,) is the only large sponge that is com- 
monly met with on sandy bottoms, but another bright yellow siliceous 
sponge, forming smooth, firm, crest-like lobes and plates, occurred on 
Edgartown beach. 
