50 THE VOYAGE OF H.M.S. CHALLENGER. 



The genus Cladocarpus was fouuilecl for a Hydi-oid obtained in tlie eastern part of 

 the North Athmtic, during one of the expeditions of H.M.S. " Poreupine." ' 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 Ix'ing 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 hydrothcca?. 



In all the species of Cladocarpus at present known, the phylactocarps are twig-like 

 appendages, more or less ramified, destitute of hydrotheciu, but richly provided with more 

 or less modified nematophores. In every instance known they spring from a hydrocladium 

 immediately behind its first or proximal hydi'Otheca, and the gonangia they are destined 

 to protect are borne either by the phjdactocarp itself or by the common stem close to the 

 origin of the hydrocladium from which the phylactocarp springs. 



Besides Cladocarpus formosus, 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. 0. Sars in the North Atlantic, and described by him under the name of 

 Aglaophenia hicuspis.^ They appear to be all inhaliitants of dei'p water. 



Cladocarpus jyectiniferus, n. sp. (PI. XVII.). 



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 length of an inch. Hydrothecfe distant, deep, narrow, nearly cylindrical, 

 with entire margin, and destitute of intrathecal ridge ; mesial nematophore small, quite 

 detached from the hydrothcca ; lateral nematophores cylindrical, overtopping the 

 hydrotheea. 



Gonosome. — Phylactocarp springing from the proximal internode of the hydrothecal 

 ramulus, and consisting of a verj^ short stem, whirh 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 Cladocarjms 

 ventrkosus of the Gulf Stream exploration. From both these species it differs in the 

 single bifurcation and pectinated branches of the ph5dactocarp, and in the fact that the 



» Report on the Hj-ilroida collected during the Expeditions of H.il.S. " Porcupine." Trans. Zool. Soc. Loncl, 1ST3, 

 Tol. viii. part 8. 



- Hydroids of the Gulf Stream, p. 49, pb. xxx.-xxxiii. ■' G. 0. Sars, loc. cit., p. 98, tali. ii. figs. 7-10. 



