352 A MONOGRAPH OF THE 



minute portions of the membranes remaining undissolved 

 and very transparent among the spicula after the applica- 

 tion of nitric acid, they were unmistakably visible, but not 

 sufficiently so to determine accurately whether the form 

 was acuate or acerate, although submitted to a linear power 

 of 600. 



5. Desmacidon .egagropila, Boiverbank. 



Halichondria .asgagropila, Johnston. 



Sponge. Sessile, massive or coating. Surface rugose or 

 corrugated. Oscula simple, dispersed, large. Pores 

 inconspicuous. Dermal membrane spiculous spicula 

 fusiformi-acuate, or sub-clavate, dispersed, occasionally 

 sub-fasciculate, very numerous, and with simple 

 contort, and reversed bihamate spicula ; rarely with 

 bidentate inequi-anchorate, and tricurvate spicula. 

 Skeleton. Spicula fusiformi-acuate or sub-clavate. 

 Interstitial membranes. Tension spicula same as those 

 of the skeleton, dispersed or sub-fasciculate. Re- 

 tentive spicula same as those of the dermal membrane ; 

 sometimes few in number, at others remarkably 

 abundant. 



Colour. Alive, red ; dried, light cream yellow. 



Habitat. Coast of Cornwall, Brighton and Hastings, 

 J. S. Bowerbank ; Guernsey and Herm, Rev. A. M. 

 Norman. 



Exami7ied. In the living state. 



At the first glance this sponge may, in the dried state, 

 be readily mistaken for B. fruticosa, which it sometimes 

 closely resembles in its external form and characters, but 

 the difference in the form of the spicula readily distinguishes 

 them. The specimens from both the localities I have 

 named are all (six) of them parasitical on small Fuci, en- 

 veloping the stem and branches, and forming an irregular 



