REPORT ON THE DEEP-SEA KERATOSA. 



81 



end a rounded or conical hypostome, and beyond it a circlet of a few short simple 

 tentacles ; their number seems to be usually (or always ?) eight. The tentacles are 

 usually highly contracted and turned inwards, rarely distinctly protruded (fig. 6, y). 



The gonophores are wanting in the great majority of the specimens examined. They 

 were, however, very distinct in a few specimens which were found in Stannophyllum 

 globigerinum and in Stannarium alatum. They are shortly pedunculate, of the 

 same ovate or club-shaped form as the hydranths, but twice or three times as long and 

 broad, without tentacles, and represent sporosacs, which in a few cases were distinctly 

 filled with eggs (fig. 6, e). The entoderm of the gonophores and hydranths exhibits 

 the same dark brown or greenish colour as that of the hydrorhiza. 



Stylactella abyssicola, n. sp. (PI. II. fig. 7). 



Habitat. — Northern and Central Pacific; symbiotic with Stannomidse and Spongelidse: 

 Stations 244, 271, 272; depths between 2300 and 2900 fathoms. 



Stylactis with a reticular hydrorhiza, the anastomosing tubes of which are of variable 

 breadth, fusiform dilatations alternating with narrower cylindrical portions. Hydranths 

 ovate, pedunculate, springing at short intervals from the hydrorhiza, provided with a 

 simple circlet of twelve to sixteen tentacles. Gonophores of about the same size as the 

 hydranths, arising scattered between them from the hydrorhiza. 



Stylactella abyssicola is much less abundant than the preceding closely-allied 

 species ; it occurs in several specimens of Psammophyllum and Stannopliyllum, taken at 

 Stations 244, 271, and 272. It is easily distinguished from the smaller Stylactella 

 spongicola by the larger size of all the parts, and the irregular formation of the tubes of 

 the hydrorhiza. These are not cylindrical and of equal breadth, but exhibit irregular 

 fusiform dilatations (often a single one between every two hydranths). Often also the 

 nodal points of the anastomosing tubes exhibit triangular dilatations. The diameter of 

 the tubes is usually between 0"2 and 0"3 mm., twice or thrice as large as in Stylactella 

 spongicola, and the chitinous perisarc is thicker than in the latter ; the network of the 

 hydrorhiza is looser and its meshes larger. 



The hydranths arise from the hydrorhiza with short peduncles, usually of their own 

 length ; they are club-shaped or ovate, 0'5 to 0*6 mm. in diameter, and bear beyond the 

 shortly conical hypostome a single circlet of tentacles (about ten or twelve to sixteen). 

 I was, however, able in a few cases only to recognise the form of the hydranths 

 distinctly (fig. 7, y). The same must be said of the gonophores, which are scarcely 

 larger than the hydranths, of the same form, but without tentacles (fig. 7, g), springing 

 from the hydrorhiza (h) scattered between the hydranths. 



(zool. chall. exp. — part lxxxii. — 1889.) Nnnn 11 



