52 THE VOYAGE OF H.M.S. CHALLENGER. 
proximal internode of a hydrocladium, bifurcating three or four times, and carrying an 
ovate, nearly sessile gonangium at the angle of every bifurcation ; branches of the phylac- 
toearp set with two series of alternately disposed cup-shaped nematophores. 
Cladocarpus formosus was also obtained during one of the expeditions of H.M.S. 
‘* Porcupine,” and has been described in the Report on the Hydroids then collected.'| The 
specimen in the Challenger collection is a very fine one, and with its long flexile pinnne 
and its phylactocarps clustered in a continuous series along their bases, forms a striking 
and beautiful object. 
The condition of the mesial nematophore of the hydrothecal internode is exceptional. 
a proximal or basal portion, which, like the 
This nematophore consists of two portions 
mesial nematophore, as usually seen, is simply continuous with the internode, and a 
distal portion, which is separated from the proximal by a transverse joint. 
No mesial nematophore is present on the internode which carries the phylactocarp. 
This springs from the internode somewhat out of the mesial line, and just below the 
hydrotheca. Cladocarpus formosus thus agrees with Cladocarpus pectiniferus in the 
evidence it affords as to the homological significance of the phylactocarp. 
Dredged at Station 236, June 5, 1875; lat. 34° 58’ N., long. 139° 30’ E.; depth, 
775-420 fathoms; bottom temperature, 2°8 C.; bottom, mud. 
Sub-family—S TA TOPLEA. 
Section—GyYMNoCARPA. 
Halicornaria, Busk, M.S. (in part). 
GENERIC CHArActerR. T'rophosome.—Hydrocladia pinnately disposed. Hydrothecee 
with mesial and lateral nematophores. 
Gonosome.—Gonangia destitute of special protective apparatus. 
The genus Halicornaria was instituted by Busk, who included under it all the then 
known Plumularian forms whose gonangia were not protected by corbule. It is here 
used in a more restricted sense, and is confined to such Plumularide as have their 
trophosome constructed on the general plan of Agluophenia, but whose gonosomes never 
develop any form of phylactocarpal apparatus. 
Halicornaria plumosa, u, sp. (P). XVIUL). 
Trophosome.—Colony attaining a height of six inches; stem simple, monosiphonic, 
springing at intervals from a creeping ramified fibre ; hydrocladia about half an inch in 
length, alternate. Hydrothecee wide, with a deep lateral notch and a strong anterior 
? Loc. cit., p. 478, pl. lxviii. 
