KEY TO BRITISH GENERA 



223 



18. - 



19. 



20. 

 21. 

 22. 

 23. 



24. 



25. 

 26. 



27. 



28. 



29. 



30. 



31. 

 32. 



f Habitat fresh water . . . . . .56 



[Habitat marine . . . . . .22 



''Megascleres include cladotyles .... Acarnus 



Megascleres include dumb-bell or sausage-shaped spicules forming the 

 main reticulum .... 



Microscleres include bipocilli 



Microscleres include diancistra . 



Megascleres include forceps 



Skeleton formed of isolated monactines vertically placed 

 ^None of the above peculiarities present 



f Skeleton fibre not echinated 

 (Skeleton fibre echinated 



f Skeleton with echinating spicules 

 \ Skeleton without echinating spicules 



rSjJongin abundant 

 (Spongin scanty 



J Fibre not echinated - 

 \ Fibre echinated 



("Fibre with a single axial series of spicules 



\ Fibres with numerous spicules arranged polyserially 



Microscleres absent 



Microscleres sigmata and'j . 



Vtoxa 



Plocamia 



. 20 



Hamacantha 



Forcepia 



Hymeraphia 



. 21 



Iophon 

 Pocillon 



28 

 30 



23 



25 



24 

 Diplodemia 



Chalina 

 Pachychalina 



. 26 



. 27 



Halichoiulria 

 Reniera 



L 



[Microscleres sigmata 



J Skeleton confused 

 (Skeleton reticulate 



/"Kind and fistulous appendages present ; microscleres sigmata Oceanapia, 

 - Xo rind; skeleton reticulate; microscleres sigmata and"! ~ -.,. 



[No rind ; skeleton reticulate ; microscleres sigmata or / 



Skeleton confused or formed of bundles of spicules with echinating 

 spined styles . . . . . .29 



. Skeleton fibrous or reticulate, or formed of short columns . 45 



Skeleton formed of a dense central axis, and columns radiating from it 

 I to the surface . . . . .52 



f Spicules of the ectosome styles .... Pytheas 



1 Spicules of the ectosome oxeas or absent . Clathrissa 



[ Main skeleton confused. Special ectosomal skeleton absent Spanioplon 



the choanosome not differing from those of the 



. 31 



Megascleres of 



ectosome . 



Megascleres of 



the choanosome 



\ Chelae absent . 

 \ Chelae present 



(Trichodragmata present 

 (Trichodragmata absent 



differing from those 



of the 



ecto- 



. 32 



. 33 



. 44 



Tedania 



. 42 



