KEV TO BRITISH GENERA 



225 



OplUitaspongia 



Axinella 



. 48 



. 49 



Myxilla 



I'Isochelae ...... Esperiopsis 



\ Anisoclielae ...... Esperella 



fFiln-es or colunuis pluniosL' . . . .46 



I Fil ires or columns ectyoniiK' . . . .47 



/'Microscleres toxa .... 



\Microscleres alij^eiit .... 



/"Skeleton reticulate .... 



\ Skeleton not reticulate 



fiMicroscleres j^ resent. Spicules of the fibre core spined 



(Microscleres absent. Sjiicules of the fibre core smooth . Lissomyxilla 



j" >rain skeleton formed of plume-like columns . . . .50 



^ Main skeleton formed of horny fil)i'e.s (ectyonine). Special dermal 

 [ skeleton wanting ..... Claihria 



JDermal skeleton contains styles only . . . Microciona 



[Dermal skeleton contains diactine spicules with or without styli 51 

 /']\Iain skeleton columns with a core of smooth oxeas Plumohalichondria 

 (Main skeleton columns with a core of spined styles . Stylostichon 

 rCentral axis contains nuich spongin. Echinating spined styli 

 I present ...... Raspailia 



I Central axis with little or no spongin. Spined styles aKsent. Pillars 



[ radiating from the axis support dermal skeleton . Ciocahjpta 



[Ground substance between chambers clear; chambers pear-.shaped or 



oval ; eurypylous ..... Sponcjelia 



54 



44. 

 45. 

 46. 

 47. 



48. 



49. 



50. 

 51. 



52. 



53. 



54. 

 55. 

 56. 



(Ground substance granular. Chambers spherical with aphodi 



/'Fibres not pithed ; sponge fan-shaped . . . Leiosella 



\ Fibres pithed ; sponge massive .... Aphjsina 



j" Chambers long, tubular, branched . . . Halisarca 



(Chambers not much longer than. broad ; not branched . Oscarella 



JAmphidiscs present ..... Ephydatia 



(Amphidisco absent ..... Spoiifjilla 



VOL. I 



