76 
THE VOYAGE OF H.M.S. CHALLENGER. 
plane passing through any one pair of hydrothecse is at right angles with the planes 
which pass through the pairs at each side of it. 
Staurotheca dichotoma, n. sp. (PI. XXXVI. figs. 1, la). 
Trophosome. — Stem strongly fascicled towards its proximal end, becoming mono- 
siphonic distally, dichotomously branched in a single plane, the branches mostly 
extended at their distal ends by a tendril-like prolongation, which when it reaches a 
neighbouring branch becomes attached to it by its extremity. Hydrothecae deep, 
nearly cylindrical, slightly tumid below, orifice circular, entire. 
Gonosome. — Gonangia elongated ovoid, narrowing below into a short peduncle 
which springs from a point just below a hydrotheca, and narrowing above into a short 
tubular prolongation, which is terminated by the small circular orifice. 
Locality. — Station 145a, off Marion Island ; depth, 85 to 150 fathoms. 
This is a well-marked form, with a somewhat flabelliform habit, caused by its 
dichotomous ramification in a single plane, with the frequent inosculations of its strong 
and rather rigid branches. It attains a height of about three inches. The pairs in 
which the hydrothecse are grouped are not regularly separated from one another by 
distinct constrictions, these occurring only at distant and uncertain intervals. 
The tendril-like prolongations of the branches usually terminate in a little sucker- 
like disc, which attaches itself to some neighbouring branch. The point of its attach- 
ment may be the walls of a hydrotheca or some part of the surface of the hydrocaulus ; 
while in some cases the tendril was seen to have entered the orifice of a hydrotheca. 
A condition closely resembling this may be seen in certain other Hydroids, as in 
Dictyocladium dichotomum of the present Report (p. 77), and in Thuiaria persocialis, 
in which the branches of the colony are frequently connected to one another by similar 
bonds of union. 1 
Dictyocladium , n. gen. 
Name from Biktvov, a net, and /cAdSos, a branch, in allusion to the net-like disposition of the 
branches. 
Generic Character. Trophosome. — Hydrocaulus consisting of a ramified monosi- 
phonic tube, the branches given off in a single plane, united to one another in such a 
way as to form a network, and with joints at distant and unequal intervals. Hydro- 
thecae more or less adnate to the branches, on all sides of which they are disposed. 
Gonosome. — Gonangia situated in the axils of the ramification. 
1 Journ. Linn. Soc. Lond. (ZooL), vol. xii. p. 271, pi. xvii. figs. 4-6. 
