4 PORIPHOKA. 



Geodia (Lamk.). Solid, permeated with sinuous 

 canals; covered with a solid crust formed of 

 globules of flint. Otherwise as Tethea. 



G. Zetlandica. Fig. 2, a slice magnified. 



Pachymatisma (Bowerbank). Fleshy, crust-like, 

 not cellular nor elastic, covered with a thick skin, 

 perforated by scattered orifices : interior beset with 

 flinty spicula both needle-shaped and starred. 



P. Johnstonia. Fig. 3, spicula magnified. 

 Halichondria (Fleming). Spongy, elastic, vari- 

 ously formed ; surface porous, studded with orifices, 

 not slimy ; substance of horny and flinty threads 

 woven into a network, or of simple flinty spicula 

 crossed and netted together, by a gelatinous flesh. 



* With a fibrous texture ; the spicula imbedded 

 in the fibres. 



t Branched or stalked. 



H. palmata. H. hispida. 



oculata. ramosa. 



cervicornis. 



tt Many-formed. 



H. Montagui. H. plumosa. 



Columbse. fruticosa. 



** With a texture like that of bread. 



f Regularly formed. 

 JE. infundibuliformis. H. ventilabrum. 



ft Shapeless. 

 \ With spicula pointed at each end. 



H. simulans. H. panicea. Fig. 4. 



cinerea. areolata. 



albescens. aculeata. 



