VIII 



KEY TO BRITISH GENERA 



225 



44. 

 45. 

 46. 

 47. 



48. 



49. 



50. 

 51. 



52. 



53. 



54. 

 55. 

 56. 



/Tsochelae . . . . . . Esperiopsis 



\Anisochelae ...... Esperella 



(Fibres or columns plumose . . . . .46 



\ Fibres or columns ectyonine . . . . .47 



/Microscleres toxa .... Ophlitaspongia 



(Microscleres absent ..... Axinella 



j Skeleton reticulate . . . . . .48 



( Skeleton not reticulate . . . . .49 



f Microscleres present. Spicules of the fibre core spined . Myxilla 



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

 [ Main skeleton formed of plume-like columns . . .50 



- Main skeleton formed of horny fibres (ectyonine). Special dermal 



skeleton wanting ..... Clalhria 



(Dermal skeleton contains styles only . . . Microciona 



(Dermal skeleton contains diactine spicules with or without styli 51 

 (Main skeleton columns with a core of smooth oxeas Plumohalichondria 

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

 'Central axis contains much spongin. Echinating spined styli 



present ...... Raspailia 



Central axis with little or no spongin. Spined styles absent. Pillars 



radiating from the axis support dermal skeleton . Giocalypta 

 I Ground substance between chambers clear; chambers pear-shaped or 



oval ; eurypylous ..... Spongelia 

 (Ground substance granular. Chambers spherical with aphodi . 54 

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



(Fibres pithed ; sponge massive .... Aplysina 



{Chambers long, tubular, branched . . . Halisarca 



Chambers not much longer than broad ; not branched . Oscar ella 

 f Amphidiscs present ..... Ephydatia 

 (Amphidiscs absent ..... Spongilla 



VOL. I 



