BRITISH SPONGIADiE. 299 



spherical cells, some containing a nucleus, while others 

 were filled with minute granules. In the living specimens 

 the tension spicula were much more abundant than in those 

 from Torquay ; in every other respect, the specimens, 

 although so various in size and form, were in perfect accord- 

 ance in every anatomical character. 



17. Isodictya fistulosa, Bowerbank. 



Sponge. Massive, sessile. Surface uneven, furnished 

 abundantly with fistulas of various sizes ; fistulas 

 simple or branched, parietes thin. Oscula terminat- 

 ing large fistulas, parietes thin. Pores conspicuous, 

 very numerous. Dermal membrane thin and pellucid, 

 furnished with a unispiculous netw r ork ; hispid, spicula 

 same as those of the skeleton ; tension spicula acerate, 

 slender, verv few in number. Skeleton. Slender and 

 delicate, rather irregular; primary lines frequently 

 only unispiculous ; secondary lines unispiculous ; 

 spicula acerate. Interstitial membranes. Tension 

 spicula acerate, slender, very few in number. 



Colour. Alive, white with a tint of pink, Rev. A. M. 

 Norman. Dried, cream wdiite. 



Habitat. Off Saint's Bay, Guernsey, Rev. A. M. 

 Norman. 



Examined. In the dried state. 



I received two specimens of this sponge from the Rev. 

 A. M. Norman. The largest was two and a half inches in 

 length by one and a half in breadth, and an inch in thick- 

 ness ; the second one was one and a half inch long, one 

 and a quarter wide, and three fourths of an inch in thick- 

 ness. The surface of the largest specimen was crowded 

 with large and small fistulas, varying in height from one 

 or two lines to seven or eight, and in diameter from one to 

 four lines. The largest ones usually terminated in one 

 large oscular orifice. The distal terminations of the smaller 



