OF THE ‘ PORCUPINE’ EXPEDITIONS. 479 
dichotomously branched, provided with numerous nematophores along their length, and 
carrying the gonangia singly at the points of bifurcation ; a gonangium is also frequently 
borne by the main stem close to the origin of a pinna. Gonangia (sex indeterminable 
in the specimens) nearly sessile, obovate. 
This very beautiful species was dredged from a depth of 167 fathoms, where the tem- 
perature of the bottom stood at 44°3 Fahr. 
DipLopteron. Gen. Char. 
Trophosome.—Hydrocaulus plumose, doubly pinnate, nematophores movable, never 
adnate to the hydrotheca; hydrothece destitute of intrathecal ridge; two pairs of 
lateral nematophores flanking the hydrotheca. 
Gonosome.—Gonangia not protected by corbule or by special ramuli. 
The genus Diplopteron is distinguished from Plumularia by its doubly pinnate rami- 
fication, and by the possession of two pairs of lateral nematophores. The doubly pinnate 
hydrocaulus of Diplopteron confers upon this genus a very striking and instantly reco g- 
nizable feature, which marks it out from Pluwmularia as distinctly as Antennularia is 
distinguished from the same genus by its verticillate ramification. - 
We know of no other member of the family in which there is more than a single pair 
of lateral nematophores. 
DIPLOPTERON INSIGNE. Plate LXVIII. figs. 2, 2%, 2°, 2°. 
Trophosome.—Stem attaining a height of about 6 inches, giving off an occasional 
branch,rooted by an entangled mass of tubular filaments, and carrying closely set, regular, 
opposite, primary pinne, which are destitute of hydrothece, and carry along their entire 
length the ultimate or hydrotheca-bearing pinne; stem and primary pinne fascicled, 
becoming single only towards the distal extremities ; ultimate pinne borne not only on 
the primary pinne but on the stem, in the intervals between the primary pinnae, closely 
set, alternate, and of nearly equal length, divided by oblique joints into internodes, and 
giving off each close to its origin a branchlet, which often bifurcates. Hydrothece deep, 
bell-shaped, free for about the distal half of their length, orifice circular, entire, slightly 
~ everted, every internode of the ultimate pinne carrying a hydrotheca. Two very large 
bithalamic lateral nematophores borne on each side of the hydrotheca and there articulated 
to a lateral process of the internode, while a pair of minute lateral nematophores is carried 
just above them, a mesial nematophore borne by the internode at the proximal side of 
the hydrotheca and another at its distal side. 
Gonosome.—Gonangia oval, with truncated summit, borne on a short two-jointed 
peduncle, which springs from the ultimate pinna-close to its origin. 
In the opposite disposition of the primary pinne of Diplopteron insigne we are 
reminded of the ramification of Plumularia catharina. In this Hydroid, however, the 
3x2 
