20 THE VOYAGE OF H.M.S. CHALLENGER. 
branches fascicled, hydrocladia springing from the branches at distant and irregular inter- 
vals, and being themselves set with rather distant, pinnately-disposed alternate hydrocladia. 
Hydrothece campanulate, every internode of the hydrocladia carrying a hydrotheca, which 
is adnate to the supporting internode for about two-thirds of its height ; lateral nemato- 
phores very short, cup-shaped, not reaching the margin of the hydrotheca; mesial 
nematophores like the lateral in form, one borne by every internode at the proximal, and 
one at the distal side of the hydrotheca. 
Gonosome not known. 
Plumularia laxa is a very remarkable form, rendered striking by its somewhat diffuse 
habit, and by the doubly pinnate arrangement of its hydrotheca-bearing ramuli. 
In this doubly pinnate condition of the hydrocladia we have a very exceptional 
character, for though it is not unusual among the Plumularidee for the ultimate hydro- 
thecal pinnze to be borne by ramuli also pinnately disposed on the main stem or primary 
branches, such ramuli rarely carry hydrothecee. The primary hydrocladia of the present 
species vary in length from about three-tenths to six-tenths of an inch ; the secondary 
hydrocladia attain a nearly constant length of about two-tenths of an inch. 
Dredged in Station 168, April 4, 1874, lat. 36° 56’ S., long. 150° 30’ E.; 120 
fathoms. 
Plumularia dolichotheca, n. sp. (Pl. I. figs. 7, 8). 
Trophosome.—Colony attaining a height of about three inches, stem irregularly 
branched, monosiphonic, hydrocladia alternate, about two-tenths of an inch in length, 
divided into internodes of unequal length, each carrying one, two, or three hydrothece. 
Hydrothec deep, thimble-shaped, adnate to their internodes by their entire height, and 
with the lateral nematophores springing from a point close to the margin of the hydrotheca; 
mesial nematophore sub-calicine only, and found only below the proximal hydrotheca of 
the internode. 
Gonosome not known. 
Plumularia dolichotheca presents several very unusual characters. It is, with the 
exception of Plumularia frutescens of the European shores, the only Plumularian with 
which I am acquainted in which more than one hydrotheca is carried by one and the same 
internode. While in the present species some of the internodes of a hydrocladium carry 
as usual only one hydrotheca, others carry two, or even three. When two or more hydro- 
theese are carried by a single internode, it is only the proximal hydrotheca which is sub- 
tended by a nematophore. This nematophore is supported on a small tubercle-like process 
of the internode, while the corresponding points below the more distal hydrothece show no 
trace of the tubercle, a fact which affords evidence that the absence of the nematophore 
is not due to its having been accidentally detached. 
Under the name of Plumularia cylindrica, Kirchenpauer describes a species—also from 
