of the Natiunul Antarctic Expedition. 21 o 



smooth, outer surface coarsely pilose. Consistence rather 

 liarrl, 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 jjt, 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, pushing up the dermal membrane, but barely projecting 

 beyond it. 



Siyicules. — Oxeas, 8355 X 4225 /a, curved at centre, sharp- 

 pointed, yigmata, 81"25 yu, long, 35" 75 /i broad, and 3"25 /a 

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

 130 jji long and 3'25 /x thick at centre, with smooth surface. 



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

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

 arrangement is like that of Phakellia ; 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/. Coulman I., 100 fath. 



Tlymedesmia 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 p,, short, 

 thick, with spines pointing backwards slightly. Ectosomal 

 tyles, 157 X 3'5 yu., straight, smooth, with oval heads, 5 jx long 

 and 4*5 yu, broad. 



Microscleres : pluridentate isancorse spatuliferse at each end, 

 with five foliate teeth, 5 p. in length, sometimes with three 

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

 central alate expansions. 



Sigmata, 9'6 p long, tyQ p broad, '5 p thick, scattered sepa- 

 rately in the choanosome. 



This new species resembles in several respects H. zetlandica^ 

 Bowerbank, but the ancorse of the latter have only three 

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

 also the ectosomal tyles are much larger, viz. 328x3*25 yu,, 

 and the spines of the acanthostyles more verticillate. Ihjme- 

 (.lesmia irritans, Thielc, from Juan Fernandez, has nearly the 



