222 



PORIFERA 



C 







d ^ f f 



Fio. 109. — Mioroscleres of Demospongiae. a, b, Sigmaspires viewed in different directions ; 

 c,d,bipocilli viewed in different directions ; e, toxaspire ; /,/', spiraster; </, sauidaster ; 

 h, ampliiaster ; i, signia ; j, diancistra ; k, isochela ; I, m, anisochelae viewed in 

 different directions ; n, cladotyle ; o, toxa ; p, forceps ; q, oxyaster ; r, spheraster ; 

 s, oxyaster with 6 actines ; t, anotlier with 4 actines ; u, another with rays reduced 

 to two (centrotylote microxea) ; v, tylote microrhabdus ; w, trichodragmata ; 

 X, oxeate microrhabdus or microxea. 



11. 

 12. 



13. 



14. 

 15. 



16. 



17. 



(^Mioroscleres sigmata .... Graniella cranium 

 [Sigmata absent, asters present ... . . .12 



TMicroscleres include spirasters . . Poecillastra compressa 



-j Microscleres include sterrasters . . . . .14 



[Mioroscleres include euasters : spirasters and sterrasters absent . 13 



TTwo kinds of euaster present .... Stelletta 



-j Microscleres include a euaster and a sanidaster or amphiaster 



[ Stryphnus ponderosus 



("Microscleres include microrhabdi . Pachymatisma johnstonia 



Gydonium milleri 



(Microscleres include many -rayed euasters 



("Some of the microscleres asters. 

 \ Microscleres absent, or not asters 



rSkeleton radiate ; asters of more than one kind 

 J. Sponge encrusting ; asters of one kind only 

 [skeleton fibrous . . . . 



[Megascleres all diactinal; chelae present 

 < Megascleres all diactinal ; chelae absent 

 [Some or all of the megascleres monactinal 



. 16 

 . 17 



Tethya 

 Hymedesmia 

 Axinella spp. 



Desmacidon 

 . 18 

 . 19 



