784 NEW GENERA OF MONAXONID SPONGES, 



renee of a slight dilatation at or near their centre. They range 

 from very rarely less than 60 up to about 110 /x in length and 

 from 2 to 6/x in diameter. The occurrence of toxa in this species 

 was not definitely recorded by Ridley and Dendy, by whom 

 they probably were overlooked owing to their scarcity. 

 hoc. — Port Jackson. 



Genus Isociella, gen. nov. 



Definition. — Desmacidonidae in which the microscleres are iso- 

 chelae palmatae (perhaps sometimes accompanied by toxa), the 

 skeleton is a sub-renieroid reticulation of smooth, typically 

 curved styli mostly free or nearly free from spongin except 

 about their extremities, and the only additional megascleres are 

 smooth slender styli (tornostyli), belonging to the category of 

 auxiliary megascleres, and occurring chiefly dermally. 



Type,!, flabellata Ridley and Dendy; the only species. 



The name originally bestowed on the species for which I es- 

 tablish this genus was Phakellia flabellata; but subsequently 

 Dendy (4), finding that the same name had previously been 

 given by Carter (2) to a Port Phillip sponge, proposed that 

 the specific name be changed to jacksoniana. In view of the 

 fact, however, that Ridley and Dendy 's species should never 

 have been assigned to Phakellia (and, indeed, would not have 

 been, had not its microscleres been overlooked), and the fact 

 that Carter's species also is not now considered to belong to 

 Phakellia, it seems to me better that the original name be ad- 

 hered to. 



Isociella flabellata differs only in one important respect from 

 certain species at present included in the genus Ophlitaspongia, 

 namely, in its non-possession of well-developed reticulating 

 spongin fibres. From the majority of the species of the latter 

 genus it further departs in the fact that its fibres are not echin- 

 ated; but this latter point of difference is probably one of only 

 minor importance. Whether, when the very needful revision of 

 the genus Ophlitaspongia is made, certain of its species will not 

 require to be associated with I. flabellata in one and the same 

 genus is perhaps open to question. It is beyond doubt, how- 

 ever, that I. flabellata and the typical species of Ophlitaspongia 

 can never be so associated. 



