294 REVISION OF THE MONAXONID SPONGES, i., 



seems mainly to be due to differences in the closeness of aggrega- 

 tion of the spicules, and particularly of the microscleres, the 

 abundance of which, throughout all parts of the sponge, constitutes 

 a marked characteristic of the species. 



The tylostyli are straight non-fusiform spicules, very gradually 

 tapering throughout the greater part of their length, and, as a 

 rule, terminating in a sharp point; their length ranges from 

 (rarely) less than 390 /x to 610 /x, while the stoutest of them are 

 11 /J. or 12/x in diameter. The spirasters are separable into two 

 groups: (i.) those which occur in great abundance throughout 

 the whole interior, and (ii.) those which are almost exclusively 

 confined to a very thin superficial layer of the sponge. The 

 former are stout, with a straight axis, and with close-set large 

 spines, which are not uncommonly as much as 20 /x in length, 

 and are frequently more or less curved in the manner of a rose- 

 thorn; inclusive of spines, these spicules measure 35 /x to 60 /x in 

 length, by 30 /x to 55 /x in breadth. The spirasters of the second 

 group, which are usually of much smaller size than the preceding, 

 are very variable in form, and perhaps are divisible into several 

 kinds; of chief importance concerning them, however, is the fact 

 that they include forms much resembling the " lophasters " of 

 Timea lophastrcea Hentschel(19), as well as forms intermediate 

 between such and spirasters of more typical shape. 



Loc. — Port Jackson. 



Papillina panis. 



In connection with this species, a difficulty presents itself 

 which, in spite of the fact that over a dozen specimens (all 

 labelled as Papillina paiiis by Lendenfeld) are at hand, cannot 

 be solved until additional material is forthcoming. The speci- 

 mens, while extremely alike in all other essential respects, are in 

 some cases provided with small oscula, in others instead with one 

 or several sieve-areas; in no observed instance do both oscula 

 and sieve-areas occur in the same specimen. So far as I can 

 see, if there is another difference between the two forms, it lies 

 in this, that, generally speaking, the oscula-bearing specimens are 

 rather of conical or wedge-shaped form, while the sieve-bearing 



