30 THE VOYAGE OF H.M.S8. CHALLENGER. 
Here, as in Schizotricha unifurcata, the first bifurcation takes place in the second seg- 
ment of the hydrocladium, this segment carrying a hydrotheca without nematophores in 
the angle of the bifurcation, and being preceded by a very short segment destitute of 
hydrotheca. 
Dredged at Station 151, February 7, 1874, off Heard Island; depth, 75 fathoms ; 
bottom, mud. 
Polyplumaria, G. O. Sars. 
Polyplumaria, G. O. Sars, Forhandl. Vidensk. Selsk. i. Christiania, 1873. 
Diplopteron, Allman, Trans. Zool. Soc. Lond., 1873. 
Generic CHaracter. Trophosome.—Hydrocladia each with an accessory hydrotheca, 
bearing ramulus, which springs from its proximal internode. , 
Gonosome.—Gonangia borne by the basal segment of the primary pinne. 
In a report on the Hydroids collected during the expeditions of H.M.S. “ Porcupine,” 
read at a meeting of the Zoological Society of London in February 1873, I described 
as a new genus and species, under the name of Diplopteron insigne, a very beautiful 
Plumularian dredged off the north-west coast of Spain, from a depth of 364 fathoms, 
during one of these expeditions.1 
G. O. Sars had, however, in the same month, but a few days earlier, described under 
the generic name of Polyplumaria, a Hydroid from the Norwegian Seas, which I believe 
2 
must be generically associated with the Hydroid of the “ Porcupine.”? The priovity of 
description thus hes with Sars, and though he does not appear to me to have seized on 
the essential characters of the genus, the name Diplopteron must sink into a mere 
synonym of Polyplumaria. 
I have here modified the diagnosis of Diplopteron as originally given, a diagnosis 
which, founded as it was on a single species, was too exclusive to admit forms which ought 
not to be generically separated. In the three species of which the genus Polyplumaria 
now consists, the most striking feature is the accessory ramulus, to which the hydrothecal 
pinne give origin. This ramulus springs from every hydrothecal pinna near to its origin, 
and is itself composed of internodes which carry hydrothece similar to those of the 
pinna from which it springs. 
Sars, it is true, does not describe the accessory ramulus as constant, but as it was 
never wanting in any of the specimens ‘examined by me, being, on the contrary, always 
very characteristic, I cannot but regard its absence from some of the branches in Sar’s 
specimens as accidental. 
* Report on the Hydroids collected during the expeditions of H.M.S. ‘ Poreupine.” Trans. Zool. Soc. Lond., 
vol. viii. p. 8. 
2 G, O. Sars, Bidrag til Kundskaben om Norges Hydroida. Forhandl. Vidensk. Selsk. i. Christiania, 1873. 
