[403] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETc. 109 
it would seem difficult for them to digest it, or get much nutriment from 
it. The supply is certainly sufficiently abundant. 
A third species of this genus, and much more beautiful than either 
of the preceding, is also common on rocky bottoms. This is the Ama- 
recium constellatum V.(p. 388,) which has already been described as 
occurring on the piles of the wharves. In deeper water, attached to 
rocks, it grows to a larger size, forming thick, hemispherical or cake- 
shaped masses or crusts, sometimes becoming somewhat mushroom-like 
by the upper parts growing out beyond the central attached portion, 
which then becomes a short and broad peduncle. It can be easily 
distinguished from the last on account of its brighter colors, the general 
color inclining to orange, and by the more irregular and complicated 
clusters of zodids. It is less abundant than either of the two preceding. 
Two other species of compound Ascidians are also abundant in this 
region, as well as farther north. These belong to the genus Leptoclinum ; 
they form thin, irregular, often broad, white, or salmon-colored incrus- 
tations over the surfaces of the rocks, shells, and other ascidians ; these 
crusts are of a firm, coriaceous or gritty texture, and have a finely 
granulous surface. Under the microscope they are seen to be filled 
with small, nearly globular particles of carbonate of lime, from which 
points project in every direction. The zodids are very minute and 
are scattered over the surface in large and scarcely distinct groups, 
. which have, however, a common cloacal orifice in the middle, but the 
several cloacal tubes or channels leading to each central orifice are 
long, with many crooked branches, reminding one of miniature rivers, 
and the zodids are arranged along these ducts and. their branches. 
One of these species, the Leptoclinum albidum, is easily distinguished 
by its chalky white color; the other, LD. luteolum, is buff or salmon- 
color. It is possible that the last may even prove to be only a colored 
variety of the former, but the very numerous specimens that I have 
collected and examined, in the living state, both in the Bay of Fundy 
and Vineyard Sound, do no not warrant their union. In these locali- 
ties both forms are about equally common, but near New Haven the 
L. luteolum has not yet been met with, though the other is not uncom- 
mon. 
The Bryozoa are very abundant on rocky bottoms at all depths. 
Some of these incrust the rocks directly, like the Hscharella variabilis, 
(p. 312, Plate XX XIII, fig. 256;) Alcyonidiwm hirsutum ; Hscharipora punc- 
tata, &c.; but even these seem to prefer other locations, and by far the 
greater number occur attached to alge, hydroids, ascidians, and dead 
shells. A large part of the species occur also in rocky pools at low- 
water mark, or attached to the Fuci and other sea-weeds between tides, 
or to the under sides of stones laid bare by low tides, and have, con- 
sequently, been previously mentioned. Others which have not yet been 
detected on the shore will doubtless be found there by more thorough 
search. 
