[731] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 437 



of the Boston Society. It consists of a large number of lon^, mostly 

 simple, but occasionally forked stems, forming a dense plume like Hu 

 united at base by an intricate mass of creeping stolons, \\liirli cover 

 what looks like the dead axis of a Gorgonia, but is most, probably a 

 dried-np black alga, and is certainly not, as Desor supposed, a part of 

 the hydroid. The stems are mostly 4 to G inches long, more or less re- 

 curved, composed of short joints, and densely covered with the secund 

 pinna), which increase in length from the base toward the tips; the 

 pinna) 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 o mra to 8 mm 

 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 uematophore 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- 

 cell. Lateral nematophores small, sessile, not so long as the upper or 

 inner side of the cells. The large, closed, oblong corbulae are irregu- 

 larly scattered among the other pinnae ; they occupy the terminal part of 

 the modified pinnae, but there are usually three or four unaltered hydra- 

 cells on the basal portion, below the corbula ; the piuna3 bearing cor- 

 bulae are somewhat shorter than the others. 



Shoals of Nan tucket, ten miles east of Sancati Head, 14 fathoms, 

 (Desor). 



PLUMULARIA TENELLA Yerrill, 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- 



