[503] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 209 
On the bottoms of loose siliceous sand the Hehinarachnius parma (p. 
362, Plate XX XV, fig. 267) is often very abundant. Several hundred are 
sometimes obtained at a single cast of the dredge. At locality 81, b, 
off the south coast of Martha’s Vineyard, in 21 fathoms, on a bottom of 
clear siliceous sand, Dr. A. S. Packard dredged a fine specimen of a 
rare and little known Holothurian, the Stereoderma unisemita. This has 
not been found before, so far as known to me, since the two original 
specimens were described twenty years ago. One of those was from the 
Banks of Newfoundland, and the other was supposed to have been from 
off Massachusetts Bay. As both the original specimens appear to have 
been lost or destroyed, this rediscovery was of considerable interest. 
This specimen was about three inches long, and half an inch in diam- 
eter, fusiform, tapering to each end; the body and suckers were pale 
flesh-color, and the integument is filled with a great abundance of small 
calcareous plates. 
Most of the Polyps and Sponges that occur on these sandy bot- 
toms are attached to the scattering dead shells and small stones or 
pebbles, and belong properly on the rocky and stony bottoms. One 
large and fine sponge seems, however, to be peculiar to the sandy 
bottoms. ‘This isa firm, siliceous sponge, with a very compact and fine 
texture. It is quite irregular in shape, but often grows in the form of 
elongated, compressed masses, attached by one edge; these masses are 
often six inches or more in length and one or two in thickness, and 
perhaps two or three high. Some of the largest specimens consist of 
two or three such crest-like plates or lobes attached together at base. 
When living the color is bright sulphur-yellow or lemon-yellow, and the 
surface is nearly smooth. One fine living specimen, of large size, was 
dredged by Dr. Packard off the southern shore of Martha’s Vineyard, at 
locality 80, b, on a bottom of clear siliceous sand. Numerous specimens 
were also found thrown on Edgartown beach. These were mostly 
bleached out white and more or less worn. This species has not yet 
been identified. I have specimens of it from the coast of Virginia. 
A very curious organism, of which the nature is still uncertain, but 
which was supposed, at the time it was taken, to belong to the sandy 
Foraminifera, was often extremely abundant in the clear siliceous sand. 
They were nearly circular, somewhat flattened or biscuit-shaped, and 
entirely covered by adherent grains of sand; except that there were 
several dark-colored, hook-like processes projecting from the circumfer- 
ence. The size was generally less than a fifth of an inch in diameter, 
and more frequently not more than .12 to.15 of aninch. When dried they 
became very friable, and the sand fell asunder at a slight touch, 
so that they then appeared like mere lumps of sand, but they retain 
their firmness when preserved in alcohol. They were often so abundant 
in the fine sand that when a dredge-full was washed through a moder- 
ately fine sieve several hundreds or thousands would sometimes remain 
in the sieve. 
