REPORT ON THE HEXACTINELLIDA. 201 



a point ; the free distal is at least twice as long, and bears short spines. At the boun-dar)- 

 of the two, in the centre of the diact, are four conical projections arranged in a circle 

 (PI. XXVIII. fig. 2). The gastral skeleton was not well preserved ; but it seemed not 

 to differ essentially from the dermah 



4. Hyalonema toxeres, Wyville Thomson (PI. XXIX.). 



Near the West Indian island St. Thomas (Station 24), lat. 18° 38' 30" N., 

 long. 65° 5' 30" W.; several specimens of a Hyalonema were dredged from a Pteropod 

 ooze ground at a depth of 390 fathoms. The species has already been shortly described 

 by Sir Wyville Thomson in his preliminary account of the Voyage of the Challenger — 

 The Atlantic. I subjoin the account there given of this form.^ 



" Two examples of the sponge-body of a very handsome Hyalonema "were sifted out 

 of the coral mud. Unfortunately, in both cases, the sponge had been torn from the 

 central coil, and the absence of the coil might have thrown some little doubt upon the 

 form and mode of finish of the complete animal ; so that it was extremely fortunate that 

 a young specimen of the same species, about 40 mm. in length, was caught in the tangles 

 quite perfect." 



" Hyalonema toxeres, Wyville Thomson, resembles closely the other known species, 

 Hyalonema lusitanicum and Hyalonema sieboldi, in general appearance and in the 

 arrangement of its parts. A more or less funnel-shaped sponge presents two surfaces, 

 covered with a network of different patterns formed by varying arrangements of large 

 five-rayed spicules. The upper concave surface shows a number of oscular openings 

 irregularly arranged, and the lower surface a more uniform network of pores, some of 

 which seem to be inhalent and others exhalent. The central axis of this sponge is 

 closely warped into the upper part of a coil of long and strong glassy spicules, 

 which, as in the other species, serve to anchor the sponge in the soft mud. Both 

 of the specimens dredged have the sponge more flattened and expanded than it 

 is in Hyalonema hisitanicum. In one of them it is nearly flat (fig. 5), forming 

 a uniform cake-like expansion, 80 mm. in length, by 70 mm. in width, and about 8 

 mm. in thickness. The upper or oscular surface is covered by an exceedingly close net- 

 work, with groups of large openings at nearly equal intervals. It is slightly raised 

 in the centre. The central elevation is followed by a slight depression, and the upper 

 wall then passes out nearly horizontally to a sharp peripheral edge, fringed with long, 

 delicate spicules, each consisting of a slender central shaft, with a cross of four 

 short transverse processes in the centre. The outer half of the central axis is delicately 

 feathered. 



"The lower surface of the sponge (fig. 6) is protected by a singularly elegant 



' Loc. cit., vol. i. p. 273. 



(ZOOL. CHALL. ESP. — PAUT LIII.— 1887.) ^SS 26 



