VIII 



KEY TO BRITISH GENERA 



225 



44. 

 45. 

 46. 

 47. 

 48. 



49. 



50. 

 51. 



52. 



53. 



54. 

 55. 

 56. 



flsoohelae 

 \Amsoclielae 



(Fibres or columns plumose 

 \Fibres or columns ectyonine 

 ("Microscleres toxa 

 \!Microscleres absent 

 J Skeleton reticulate 

 \ Skeleton not reticulate 



j" Microscleres present. Spicules of the fibre core spined 

 \ Microscleres alfcent. Spicules of the fibre core smooth 

 [Main skeleton formed of plume-like columns 

 4 Main skeleton formed of horny fibres (ectyonine). 

 [ skeleton wanting .... 



(Dermal skeleton contains styles only 



Eqieriopsis 

 Esperella 

 . 46 

 . 47 

 OpUitaspongia 

 Axinella 

 . 48 

 . 49 

 Myxilla 

 Lissomyxilla 

 . 50 

 Special dermal 

 Glaihria 

 Microciono, 

 \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 

 rCentral axis contains much spongin. Eohinating spined styli 

 present ....•• Raspailia 

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

 radiating from the axis support dermal skeleton . Giocalypta 

 TGround substance between chambers clear ; chambers pear-shaped or 

 J oval; eurypylous. .... Spongelia 



[ Ground substance granular. Chambers spherical with aphodi . 54 

 /Fibres not pithed ; sponge fan-shaped . . ■ Letosella 



\Fibres pithed ; sponge massive . . ■ ■ Aplysina 



/Chambers long, tubular, branched . . • Halisarca 



\ Chambers not much longer than broad ; not branched 

 JAmphidiscs present .... 

 \Amphidiscs absent .... 



Ephydatia 

 Spongilla 



VOL. I 



