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



Gellius glacialis, var. nivea, nov. (PI. VIII. fig. 8 ; PI. XIII. figs. 4, 12). 



Sponge (PI. VIII. fig. 8) incrusting, amorphous, in the form of a small round cushion, 

 filling up the angle between the branches of a Polyzoon. Diameter about 12 mm. 

 thickness about 8 mm. Colour in the dry state white ; appearance like fleecy snow, 

 whence the varietal name. Texture brittle. Surface even, but rough, owing to the 

 dermal membrane being absent. Oscula and 2^ores unknown. 



Skeleton. — A very loose reticulation of oxeote spicules, not united together into 

 distinct fibres. This reticulation is very like that of Gellius Jlagelli/er, nobis, but in 

 that species it is just possible to speak of spiculo-fibre, while here the reticulation is so 

 loose that the term is no longer admissible ; there is, however, but little real difierence in 

 this respect between the two. 



Spicules. — (a) Megasclera; oxea (PI. XIII. fig. 4), tapering rather suddenly to a 

 sharp point at each end. Slightly curved and measuring 0"53 by 0'02 mm. (6) 

 Microsclera are present in the form of numerous sigmata (PI. XIII. fig. 12) of the usual 

 shape, but attaining a very great size, up to 0'145 by 0"0063 mm. Smaller ones are 

 also present, probably young forms of the others. 



It will be seen that both in the arrangement and form of the mes-asclera and in 

 the great size of the sigmata this variety of the species comes very near to Gellius 

 Jlagelli/er, nobis ; it is, however, easily distinguished by the very different shape and 

 superior thickness of the large sigmata. The sponge has unfortunately been dried, so 

 that the skeleton is the only part the structure of which can be satisfactorily made out. 

 Judging from its small size it is probabl}^ a young form. 



Xoe«%.— Station 145, December 27, 1873; lat. 46° 43' 0" S., long. 38° 4' 30" E.; 

 Prince Edward Island ; depth, 140 fathoms ; bottom, volcanic sand. One small specimen. 



Gellius fiagellifer, Eidley and Dendy (PI. XIII. figs. 5, 10). 



1886. Gelliiis fiagellifer, Eidley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. xviii. p. 333. 



Sponge massive, sessile, roughly triangular in shape,^ the side of the triangle 

 measuring a little over 25 mm. in length ; thickness of the sponge from the centre of 

 one triangular surface to the centre of the other 16 mm. Colour in spirit pale greyish- 

 yellow. Texture soft, brittle. Surface even but shghtly rough, probably owing to 

 the dermal membrane having been in most parts rubbed off. Dermal membrane thin 

 and transparent, with numerous scattered i^ores about 0"07 mm. in diameter. Only one 

 distinct osciilum visible at one side. A second specimen, very likely only a fragment, 

 is cylindrical, 29 mm. long by 8 mm. in diameter. 



Skeleto7i. — There is a dermal netw^ork of spiculo-fibre indistinguishable from the 

 spiculo-fibre forming the skeleton at large. The deeper skeleton is composed of a loose, 



^ Perhaps a young specimen, incipiently lobose. 



