[731] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 4217 
of the Boston Society. It consists of a large number of long, mostly 
simple, but occasionally forked stems, forming a dense plume-like cluster, 
united at base by an intricate mass of creeping stolons, which cover 
what looks like the dead axis of a Gorgonia, but is most probably a 
dried-up black alga, and is certainly not, as Desor supposed, a part of 
the hydroid. The stems are mostly 4 to 6 inches long, more or less re- 
curved, composed of short joints, and densely covered with the secund 
pinnie, which increase in length from the base toward the tips; the 
pinne arise from every joint, and form two close alternating rows along 
the inner side of the stems ; they are directed upward, and more or less 
curved inward, toward each other, near the tips, and mostly 5™™ to 8™™ 
in length, composed of short, stout, oblique joints, not twice as long as 
broad. Hydra-cells deep, slightly flaring, rising at an angle of about 
45°, attached only at base, the upper side less than half as high as the 
lower, border strongly dentate: one slender median denticle on the up- 
per edge ; four lateral ones on each side, of which three are subequal, 
triangular, rather wide, obtuse, with rounded intervals; the lower or 
outer lateral one is twice as long, rather acute; the single odd median 
one, on the outer margin, is equally long and more slender, and usually 
bent upward. A single large tubular median nematophore is attached 
to the outer side of the cell, along most of its length, but separated at 
the end, which is obliquely truncate, with the aperture on the inner 
side, its tip nor extending beyond the long lateral denticles of the hydra- 
eell. Lateral nematophores small, sessile, not so long as the upper or 
inner side of the cells. The large, closed, oblong corbule are irregu- 
larly scattered among the other pinne; they occupy the terminal part of 
the modified pinna, but there are usually three or four unaltered hydra- 
cells on the basal portion, below the corbula; the pinnie bearing cor- 
bulz are somewhat shorter than the others. 
Shoals of Nantucket, ten miles east of Sancati Head, 14 tathoms, 
(Desor). 
PLUMULARIA TENELLA Verrill, sp. nov. (p. 407.) 
Stems clustered, simple, slender, 1 to 2 inches high, horn-colored ; 
branches alternate, very slender, not very long, mostly unbranched, 
placed toward one face of the stem, inclining forward, and ascending 
at an angle of about 45°, and originating from the alternate joints of the 
stem, the internodes being longer than the joints that bear branches ; 
at one side of the base of each branch there is a hydrotheca and accom- 
panying nematophores; the internodes of the,stem also bear one or two 
nematophores. The basal segment of each branch is short ; the rest 
are of three kinds ; every third one is usually stouter, and bears a hydro- 
theca; just in front of each hydrotheca there is usually a very short 
segment, scarcely longer than broad, and sometimes indistinct, destitute 
of nematophores; then follows a much longer, slender segment, five or 
six times as long as broad, articulated by a very oblique joint at its dis- 
