50 : THE VOYAGE OF H.M.S. CHALLENGER. 
The genus Cladocarpus was founded for a Hydroid obtained in the eastern part of 
the North Atlantic, during one of the expeditions of H.M.S. ‘ Porcupine.”? The same 
species also occurs in the collection of the Challenger. The essential characters of the 
genus are found in the nature of the phylactocarp, which differs from that of every other 
phylactocarpal Plumularidan in the fact of its not being a transformed hydrocladium, but 
a special appendage which springs from the hydrocladium. The hydrocladium itself has 
undergone no essential modification, the greatest change which in any case takes place 
consists in a greater or less diminution of its length, caused by a reduction in the number 
of its internodes and hydrothecee. 
In all the species of Cladocarpus at present known, the phylactocarps are twig-like 
appendages, more or less ramified, destitute of hydrothece, but richly provided with more 
or less modified nematophores. In every instance known they spring from a hydrocladium 
immediately behind its first or proximal hydrotheca, and the gonangia they are destined 
to protect are borne either by the phylactocarp itself or by the common stem close to the 
origin of the hydrocladium from which the phylactocarp springs. 
Besides Cladocarpus jformosus, the original species of the ‘ Porcupine,” the 
Challenger collection contains another fine species. Three other species of the genus are 
among the Hydroids dredged during the exploration of the Gulf Stream by the United 
States Coast Survey,’ while to the same genus I must refer a Plumularidan dredged 
by G. O. Sars in the North Atlantic, and described by him under the name of 
3 
Aglaophenia bicuspis.’ They appear to be all inhabitants of deep water. 
Cladocarpus pectiniferus, n. sp. (Pl. XVIT.). 
Trophosome.—Colony attaining a height of about six inches ; stem slender, monosi- 
phonic, simple, springing from a tuft of tubular filaments ; hydrocladia alternate, distant, 
attaining the leneth of an inch. Hydrothecee distant, deep, narrow, nearly cylindrical, 
with entire margin, and destitute of intrathecal ridge ; mesial nematophore small, quite 
detached from the hydrotheca; lateral nematophores cylindrical, overtopping the 
hydrotheca. 
Gonosome.—Phylactocarp springing from the proximal internode of the hydrothecal 
ramulus, and consisting of a very short stem, which immediately divides into two jointed 
and pectinated branches which carry the gonangia on their sides, 
The present species is closely allied to Cladocarpus dolichotheca and Cladocarpus 
ventricosus of the Gulf Stream exploration. From both these species it differs in the 
single bifurcation and pectinated branches of the phylactocarp, and in the fact that the 
1 Report on the Hydroida collected during the Expeditions of H.M.S. “ Porcupine.” Trans. Zool. Soc. Lond., 1873, 
rol. vill. part 8. 
* Hydroids of the Gulf Stream, p. 49, pls, xxx,-xxxiii, 3 G. O. Sars, loc. cit., p. 98, tab. ii. figs. 7-10, 
