KEY TO BRITISH GENERA 



223 



18. 

 19. 



20. 

 21. 

 22. 

 23. 



24. 



25. 

 26. 

 27. 



28. 



29 



("Habitat fresh water 

 \ Habitat marine 



'Megasderes include cladotyles 



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



main reticulum . . . 



IMicroscleres include bipocilli 

 Microscleres inchide diancistra . 

 Megascleres include forceps 



Skeleton formed of isolated monactines vertically placed 

 None of the above peculiarities present 



I" Skeleton fibre not echinated 

 \Skeleton fibre echinated 



("Skeleton with echinating spicules 

 \ Skeleton without echinating spicules 



f Spongin abundant 

 \Spongin scanty 



("Fibre not echinated 

 \ Fibre echinated 



("Fibre with a single axial series of spicules 

 \Fibres with numerous spicxiles arranged polyserially 



Microscleres absent .... 



. 56 

 . 22 



Acarnus 



Plocamia 



. 20 



Hamacantha 



Forcepia 



HymerapMa 



■ 21 



lophon 

 Pocillon 



28 

 30 



23 



25 



24 

 Diplodemia 



Ghalina 

 Pachychalina 



. 26 



. 27 



Halichondria 

 Reniera 



30 



31 



32 



i 



J Microscleres sigmata andV 



[Microscleres sigmata or J 



J Skeleton confused 

 [Skeleton reticulate . 



("Eind and fistulous appendages present ; microscleres sigmata Oceanapia 

 J No rind ; skeleton reticulate ; microscleres sigmata andV^^^ Gellius 

 [No rind ; skeleton reticulate ; microscleres sigmata or / 



Skeleton confused or formed of bundles of spicides 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 



^ to the surface . • • ■ ■ .52 



("Spicules of the ectcsome styles . . ■ • Fytheas 



. \ Spicules of the ectosome oxeas or absent . . Clathnssa 



[Main skeleton confused. Special ectosomal skeleton absent Spamoplon 



{Megascleres of the choanosome not differing from those of the 

 ectosome . . ■ • • 



Megascleres of the choanosome differing from those 

 some 



/■ Chelae absent . 

 \ Chelae present 



JTtioliodragmata present 

 ■ [Trichodragmata absent 



of the 



31 



ecto- 

 . 32 



. 33 



. 44 



Tedania, 

 . 42 



