of the National Antarctic Expedition. 273 



smootli, outer surface coarsely pilose. Consistence rather 

 hard, but flexible. Colour in spirit greyish drab. Inner 

 surface with numerous small oscules, each about 1 mm. in 

 diameter ; outer surface pilose, with dermal membrane per- 

 forated by round pores 95 fx in diameter. 



Skeleton. — On inner surface formed of close-set longitu- 

 dinal lines joined by cross-bars, and giving off tufts of fibres, 

 which proceed outwards at right angles to the outer sur- 

 face, ])ushing up the dermal membrane, but barely projecting 

 beyond it. 



/Spicules. — Oxeas, 83;Vr)X •12-2;j /x, curved at centre, sharp- 

 pointed. Sigmata, 81'25 /i long, 35"75 /x broad, and '6 25 /x 

 thick, often with an angular bend at centre of shaft. Toxa, 

 130 fx long and 3"!25 fx thick at centre, with smooth surface. 



Tliis species bears in its outward aspect a very close re- 

 semblance to cup-shaped species of Phakeilia ; also the skeletal 

 arrangement is like that of Phakeilia ; the oxeas, sigmata, 

 and toxa are those of a typical Gellius. The Axinellid genus 

 Sigmaxinella, Dendy, which has microscleres in the form of 

 sigmata, has styles for megascleres. 



Locality. Cuulman 1., 100 fath. 



Hymedesmia exigua, sp. n. 



The sponge forms a thin translucent greyish-white crust, 

 about 5 mm. in diameter, on a stone. The surface is smooth, 

 and the substance of a fleshy consistence. 



Skeleton. — The choanosome contains scattered short acantho- 

 styles, and the dermal membrane tangential tyles isolated 

 or in bundles of a few. 



Spicules. — Megascleres : acanthostyles, 94 X 19 [x, short, 

 thick, with spines pointing backwards slightly. Kctosomal 

 tyles, 157 x 3*5 fx, straight, smooth, with oval heads, 5 /* long 

 and 4-5 //. broad. 



Microscleres : pluridentate isancor?e spatulifera? at each end, 

 with five foliate teeth, 5 fx in length, sometimes with three 

 or four ; shaft deeply curved, 2*5 M thick, sometimes with 

 central alate expansions. 



Sigmata, 9'G [x long, 5*6 ix broad, '5 jx thick, scattered sepa- 

 rately in the choanosome. 



This new species resembles in several respects U. zetlandica, 

 Bowerbank, but the ancovse of the latter have only three 

 teeth, the sigmata are much longer (51 fx) and in sheaves ; 

 also the ectosomal tyles are much larger, viz. 328 X 3*25 /a, 

 and the spines of the acanthostyles more verticillate. Ui/me- 

 dcsmia /7'r/V(f/Ks, Thiele, iVom Juan Fernandez, has nearly the 



