SILICIOUS AND HORNY SPONGES WILSON. 285 



speak, in Nethea, in which genus the triaenes are not localized at the 

 surface but are scattered through the sponge. (Topsent, 1902&, p. 11.) 



Family STELLETTIDAE. 



SteTlettidae Sollas, 1888; Lendenfeld, 1003. 



The tetraxon megascleres are triaenes, radially arranged. With 

 euasters, some of which are slightly modified in certain species in the 

 direction of streptasters, but without true streptasters or sterrasters. 

 In addition, microrhabds or sanidasters occur in some species. 



Dendy (1916) would include in the Stellettidae certain reduced or 

 epipolasid genera, Asteropus Sollas and Jaspis Gray. I believe it is 

 best, considering all the purposes for which our classification schemes 

 are used, not to follow this practice but to retain the Epipolasidae 

 as a hadromerine (astromonaxonellid) family, thus adhering to ob- 

 jective fact rather than to deductive reasoning. Of course, as every- 

 one knows, it is not possible to do this always and at the same time to 

 avoid practices that are artificial. A case in point is that of Geodin- 

 (11a spherastrosa (see p. 322), a species strictly without triaenes and 

 yet one which is undoubtedly assignable to the Greodiidae, since it 

 has all the other very characteristic marks of this family and since 

 the monaxon megascleres are shown by certain vestiges, still recogniz- 

 able, to be reduced triaenes. 



Subfamily Stellettinae. 



Stellettinae Lendenfeld, 1006, p. 253. 



Without a special cloacal tube. 



In addition to the genera represented in the collection {My nostra, 

 Stelletta, and Edonemia) the subfamily includes the following: 



Astrella Sollas (1888, p. 136). Merged in Stelletta by Lendenfeld 

 1903. 



Anthastra Sollas (1888, p. 138). Merged in Stelletta by Lendenfeld 

 1903. 



Dragmastra Sollas (1888, p. 187) emended, Dendy (1916. p. 237). 



Aurora Sollas (1888, p. 187). See Dendy 1916, p. 242, for an impor- 

 tant discussion of this genus. He would include certain species (of 

 Aurora) strictly without triaenes but which he regards as reduced 

 or " epipolasid " forms — namely, forms in which the monaxon 

 megascleres more or less obviously represent triaenes in which the 

 clads have degenerated. These species are : Coppatias {Rhab- 

 ■dastrella) distinctus Thiele (1900), Diastra sterrastrosa Row 

 (1911), and Aurora cribriporosa, new species. I prefer to retain 

 Diastra Row, and to merge Rhabdastrella Thiele in Jaspis {Cop- 

 patias). See Hadromerina. 



