406 REVISlO>r OF THE MONAXONID SPONGES, iil., 



(g). Slender toxa, 30-63 /x long ; occurring singly and in 

 dragmata. 



(h). Slender microxea, 20-35 /x long; occurring in dragmata, and 

 also singly. 



Loc. — Western Australia. 



Remarks. — M. ridleyi is the fifth species of the genus known 

 to possess isochelse, the other four heing M. plumosa Carter, M. 

 parishi Bowk., M. isochela Hentschel(20), and M. pectinicola 

 Hentschel(20); an undescribed sixth is represented in the British 

 Museum by a specimen labelled (by Lendenfeld) with the MS. 

 name '^EspereUa australisJ' On the assumption that the toxa 

 observed by Ridley(33) in Bowerbank's preparations of M. pectini- 

 cola were proper, all these species likewise agree in the possession 

 of toxa, besides showing a very close correspondence (with each 

 other) in the remaining features of their spiculation. 



EsPERELLA SERPENS. (Pl.xxiv., fig. 6; and text-tig. 14). 



Description. — The single type-specimen (as also a fragment 

 labelled Esperella serpens from the British Museum) corresponds 

 satisfactorily to Lendenfeld's description of the species. It is a 

 cake-shaped sessile sponge, measuring 80 mm. in length, 50 mm. 

 in breadth, and about 25 mm. in height, the visible external por- 

 tion of Avhich is formed by confusedly anastomosing irregular lax 

 processes, usually more or less round in cross-section and averiaging 

 2 or 3 mm. in diameter. On cutting through the specimen, the 

 more compact — and, at first sight, seemingly solid — interior is 

 found to have a structure affording reason for believing it to have 

 resulted through the very complete and intimate fusion of what 

 originally were similar processes. In alcohol (perhaps largely 

 owing to imperfect preservation) the consistency is soft, almost 

 pulpy: and the whole sponge is exceedingly fragile. The colour 

 is a dull faintly yellowish pale grey. The dermal membrane is 

 thin and delicate. Oscula were not observed. 



The main skeleton is exceedingl}^ reduced, being composed 

 almost entirely of sparsely and quite irregularly scattered slender 

 tylostyli. The dermal skeleton, although much better developed, 

 is also comparatively scanty; it consists of ramifying spicular 



