40 THE VOYAGE OF H.M.S. CHALLENGEE. 



Gellius cardmis, var. magellanica, nov. (PL XIII. fig. G). 



Sponge massive, sessile. Shape elongately oval, size about 62 mm. by 25 mm.; 

 tapering irregularly towards each end. Colour in spirit pale brownish-yeUow. Texture 

 rather firm and compact, but brittle. Surface glabrous but uneven. Dermal membrane 

 distinct, rather coarse. Oscula irregularly scattered over the upper surface. 



Skeleton. — (a) Dermal ; in some parts a unispicular reticulation of oxeote spicules ; 

 in other parts broad bands of loose spiculo-fibre are also present, (b) Mai?i ; a reticula- 

 tion of loose but distinct spiculo-fibre, main fibres running more or less vertically to the 

 surface and others at right angles to these ; but these two main directions are only very 

 roughly marked out. The fibres themselves are about 0"175 mm. in diameter. 



Spicules. — (a) Megasclera; stout oxea (PL XIII. fig. 6), tapering rather gradually to 

 a rather blunt point at each end ; measuring about 0"49 by 0*022 mm. (6) Microsclera ; 

 numerous very small sigmata measuring 0"019 by 0"0008 mm. 



This is a very interesting geographical variety from the Strait of Magellan. The 

 main features in which it differs from the type specimens of Gellius carduus concern 

 the oxeote spicules which, in the variety in question, are much more pointed and a good 

 deal shorter than in the type ; the skeleton-fibre also seems to be better developed. 



LocalitT/.— Station 311, January 11, 1876; lat. 52° 45' 30" S., long. 73° 46' W.; 

 Strait of Magellan, west end ; depth, 245 fathoms ; bottom, blue mud ; bottom tempera- 

 ture, 46°*0. One specimen. 



Gellius Isevis, Ridley and Dendy (PL XIII. fig. 8). 



1886. Gellius Ixvis, Ridley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol xviii. p. 333. 



This species agrees very closely in spiculation with the typical specimens of 

 Gellius carduus. The spicules, both megasclera (PL XIII. fig. 8) and microsclera, 

 are of the same shape and almost of the same size. The chief points of difference 

 concern the surface and size of the specimens. The surface is not nearly so uneven as 

 in Gellius carduus; the oscula are large and round, and their margins flush with the 

 general surface of the sponge. The specimens are also much larger than the types of 

 Gellius carduus, the largest being massive and cake-like, and measuring 143 mm. in 

 length, 81 mm. in breadth, and about 31 mm. in average thickness. 



Two specimens were obtained, both of which were infested by a very beautiful 

 and peculiar little Isopod, which occurs also on a fine Esperella from the same Station. 



Zoca%.— Station 320, February 14, 1876; lat. 37° 17' S., long. 53° 52' W.; oft' 

 the mouth of the Rio de la Plata ; depth, 600 fathoms ; bottom, green sand ; bottom 

 temperature, 37°'2. Two fine specimens. 



