of Otc Nal'ional Antarctic Expedition. 275 



but the first and tliivd sjiecies are encrusting, and the second 

 has long slender branches. 



Dredged off Coulraan I., 100 fath. 



Lissom YxiLLA, Hanitsch. 



This genus was established by Hanitsch * to include 

 Ectyonine Sponges Avith filnx'S having a core of smooth 

 styles echinated by acanthostyles with special ectosouial 

 megascleres, and with or without microscleres. Unfortunately 

 the species he selected as type o£ the genus {Tethea spi- 

 nosa, Bowerbank) in no way fell in with the definition, since, 

 as Topsent f points out, this species has neither echinating 

 spicules nor special ectosomal spicules^ and Topseiit refers 

 Lissomyxilla to the limbo of useless names. Among the 

 ' Discovery ' sponges, however, is a specimen which tits in 

 with Hanitsch's definition of Lissomyxilla, which runs : — 

 *' Skeleton fibres of the choanosome formed of smooth mon- 

 actinals echinated by spined styles. i\legascleres of the 

 ectosome smooth diactinals or monactinals. Microscleres 

 (isochelas &c.) may be present." Accordingly I propose to 

 revive the name. 



Lissomyxilla Ilanitschi, sp. n. 



There are two much-worn species of this sponge of a dark, 

 dirty -grey colour, and a third young small specimen, whitish 

 in colour, growing on a specimen of llornera. The largest 

 specimen is 4 cm. high and 5 cm. in diameter at the base ; 

 the dermal membrane is worn away, exposing several open- 

 ings of exhalant canals, 4 mm. in diameter. The dermal 

 membrane of the smallest specimen is transparent, smooth, 

 and raised ii[) at one place into a small conical oscule, with 

 radial tangential spicules in its walls. 



The skeleton of the choanosome is formed of branching 

 fibres on an average about 150 /a thick, echinated by spined 

 styles in an obscurely verticillate manner, the whole skeleton, 

 as seen in sections, having a somewhat confused appearance. 

 The ectosomal spicules partly proceed obliquely from the 

 main fibres to the dermal membrane, and partly lie tangenti- 

 ally in that membrane. 



Spicules. — Megascleres : styles, 500 x 19 fx, smooth, curved 

 near the head, sharp-pointed. Echinating acantliostyles, 



* Trans. Liverpool Biol. Sue. vol. viii. p. 194 (1894). 



t Arcliiv. Zool. E.xp. et Gcu. (•"]) tome viii. p. '205 (1900). 



