REPORT ON THE DEEP-SEA KERATOSA 77 



usually contracted, turned inwards to the mouth, and difficult to distinguish, but some- 

 times they were prominent over the conical hypostome, and formed a single circlet, 

 composed of eight to sixteen cylindrical tentacles (PI. II. figs. 5-7, y). The entoderm 

 of the hydranths exhibited the same dark coloration as that of the hydrorhiza. 



The hydranths of Halisiphonia spongicola (a Campanularian Hydroid allied to Lafoea) 

 were not preserved in the few specimens of Stannomida? in which it occurred ; but in 

 this case the chitinous hydrotheca, very similar to that of Halisiphonia megalotheca 

 (Allman), permitted me to recognise the genus of the symbiotic Hydroid. 



Gonophores. — Sexual zooids bearing eggs in their walls were observed in both species 

 of Stylactis, but not in Halisiphonia ; they were, however, rare, and not found in the 

 majority of hydrosomes. They were in both species ovate or club-shaped naked bodies, 

 which arose from the hydrorhiza between the hydranths (PI. II. figs. 6, 7, g). Halisi- 

 phonia exhibited a few chitinous oviform gonangia (PI. IV. fig. 9, g). The entoderm of 

 the gonophores in Stylactis is of the same dark phseodiuni-like colour as that of the 

 hydrorhiza and the hydranths. 



Halisiphonia spongicola, n. sp. (PI. IV. fig. 9). 



Habitat. — North Pacific, Station 241 ; depth, 2300 fathoms. Central Pacific, Station 

 272 ; depth, 2600 fathoms ; symbiotic with Stannoma and Psammophyllum. 



Halisiphonia with a reticular hydrorhiza, the anastomosing tubes of which are 

 cylindrical, of equal breadth. Hydranths probably cylindrical, enclosed in a slender 

 cylindrical hydrotheca, which arises by a thin and short pedicle from the hydrorhiza. 

 Gonangia ovate, with a circular opening, twice as broad and about as long as the 

 hydothecse, arising scattered between them from the hydrorhiza. 



Halisiphonia spongicola is very similar to Halisiphonia megalotheca, described by 

 Allman. 1 This latter species was collected by the Challenger at Station 1 60 (south of 

 Australia), at a depth of 2600 fathoms. Allman gives the following description of it : — 

 "Hydrocaulus a creeping and adherent tube which supports at irregular intervals pedun- 

 culated hydrotheca?. Hydrotheca? very large, cylindrical, gradually passing below into 

 the long smooth cylindrical peduncle. Gonangia spathuliform, borne on short peduncles, 

 and with the summit opening by a long narrow transverse slit." 



The trophosome of Halisiphonia spongicola is very similar to the figure given by 

 Allman, but its network is much more developed, and traverses the whole body of 

 Psammophyllum flustraceum (p. 52, PI. IV. fig. 5), and probably also that of 

 Stannoma coralloides (PI. III. fig. 5) ; from the surface of the former is prominent 

 only the distal part of the hydrotheca?, with their openings. It seems, therefore, more 

 reasonable to call the trophosome of this symbiotic species hydrorhiza (as in Stylactis), 



1 Zool. Chall. Exp., pt. lxx. p. 31, pi. xvi. figs. 1, la. 



