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



proximal iuternode of a hydrocladium, bifurcating three or four times, aud carrying an 

 ovate, nearly sessile gonangium at the angle of every bifurcation ; branches of the phylac- 

 tocarp set with two series of alternately disposed cup-shaped nematophores. 



Cladocarpus formosiis was also oljtained during one of the expeditions of H.M.S. 

 " Porcupine," and has been described in the Eeport on the Hydroids then collected.^ The 

 specimen in the Challenger collection is a very fine one, and with its long flexile pinunaj 

 and its phylactocarps clustered in a continuous scries along their bases, forms a striking 

 and beautiful object. 



The condition of the mesial ncmatophorc of the hydrothccal internode is exceptional. 

 This nematophore consists of two portions — a proximal or basal portion, which, like the 

 mesial nematophore, as usuall}^ seen, is simply continuous with the internode, aud a 

 distal portion, which is separated from the proximal Ijy 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 formosiis 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 tatoplea. 



Section — Gymnocarpa. 



Halicovnaria, Busk, M.S. (in part). 



Generic Chakacte?.. Trojjhosoriw. — Hydrocladia pinnately disposed. Hydi-othecee 

 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 corbulse. It is here 

 used in a more restricted sense, and is confined to such Plumidaridse as have theii- 

 trophosome constructed on the general plan of Aghiophcnia. l)ut whose gonosomes never 

 develop any form of phylactocarpal apparatus. 



Halicornaria ptlumosa, n. sp. (PL XVIIL). 



Trophosome. — Colony attaining a height of six inches ; stem simple, monosiphouic, 

 springing at intervals from a creeping ramified fibre ; hydrocladia about half an inch in 

 length, alternate. Hydrothecse wide, with a deep lateral notch and a strong anterior 



' Loc. cit., p. 478, pi. Ixviii. 



