20 SYDNEY J. HICKSON anp F. H. GRAVELY. 
Each internode of a pinnule bears one hydrotheca at its distal extremity, but 
each internode of a branch bears three hydrothecze, one at the distal extremity, and 
the other two at intervals of one-third and two-thirds from the proximal end. 
The hydrothecee of the pinnules (fig. 19) are about 0°5 mm. in depth, 0°22 mm. 
in their greatest diameter, and 0°17 mm, in diameter at the mouth, and have three 
opercular flaps (fig. 19, op.) 0°09 mm. in length. They are somewhat shorter than 
this in the proximal regions of the pinnules. The two proximal hydrothece of 
the internodes of the branches are decidedly shortened as regards that part of 
their length which is not adnate. The distal hydrotheca of each internode of the 
branches is nearly straight and barrel-shaped. A single straight hydrotheca, which is 
not adnate to any part of a hydrocaulus, is situated between the bases of each pair of 
branches (fig. 20, /th.). Apart from these, the main axis bears no hydrothece. 
A remarkable feature of the hydranths is the presence of a loose sheath of 
ectoderm (fig. 19, ect.) enveloping the base. The hypostome is conical and 
surrounded by about fifteen tentacles. 
Gonosome.—Only female gonothece (fig. 19, gth.) have been observed. They 
are 1:0 X 0°5 mm. in size, ovate, smooth, sessile, and attached below the bases 
of the hydrothecee of the pinnules. The gonothecze are all empty, none of the 
gonophores being preserved. The planulz are developed in spherical or somewhat 
pear-shaped acrocysts (fig. 19, ae.), 0°4 mm. in diameter. 
This species seems to be quite distinct from any that has yet been described. 
SERTULARELLA PLECTILIS. 
(Plate IIL, fig. 21.) 
Localities.—W.Q., No. 6 hole, February 15th, 1902; 130 fms. W.Q., McMurdo 
Bay, February 20th, 1902; 20 fms. 
Several large, detached, tangled masses of this hydroid were found in the first- 
named locality; but in the second locality only a single small colony 12 mm. in 
height attached to the stem of Campanularia verticillata was obtained. 
LHydrosome. —The hydrocauli are all extremely slender, not exceeding 0°12 mm. 
in diameter, irregularly branched, and—as they reached us—in an inextricable tangle. 
The internodes are about 0°6 mm. in length. The branches arise immediately below 
the hydrothece (fig. 21). A single hydrotheca is situated at the distal end of 
each internode. As many of them are reduplicated (fig. 21, 7. /th.), they vary 
considerably in length. The original length of each hydrotheca appears to be 
0°4 mm., but one showing four reduplications is 0°6 mm. The greatest diameter 
is 0°15 mm., and at the mouth 0°13 mm. The wall is adnate to the hydrocaulus 
for about one-third of its original length. It is extremely thin. The margin has 
three opercular flaps, 0°06 mm. in length. About fifteen tentacles surround the 
bluntly conical hypostome of the hydranths. 
