268 A MONOGRAPH OP THE 



The terminally spined sub-fusiform cylindrical spicula are 

 more sparingly dispersed in the interstitial membrane than 

 they are in the dermal one, and they are very rarely col- 

 lected in fasciculi. 



The compressed cytoblasts or cells of the sarcode are 

 abundant throughout the whole of that substance; some 

 of them exhibited a nucleated appearance. The diameter 

 of an average sized one that I measured was a^ard inch. 



I have since received this species from Professor Dickie 

 who dredged it in Strangford Lough. This specimen coated 

 a valve of Pecten opercularis for the thickness of rather 

 more than the eighth of an inch, and I have also obtained 

 numerous specimens coating the valves of Pecten opercu- 

 laris from the Diamond Ground, off Hastings, the sponge 

 in some cases being nearly three fourths of an inch in 

 thickness, and in others not exceeding the thickness of 

 stout paper; when in the latter state, the sponge may 

 be readily mistaken for a Hymeniacidon. 



26. Halichondria albula, Bowerbank. 



Sponge. Coating, very thin; surface smooth and even. 

 Oscula simple, dispersed. Pores inconspicuous. 

 Dermal membrane translucent, abundantly spiculous ; 

 spicula equally dispersed ; acuate, entirely spined, large, 

 and stout ; spines conical, stout, and long. Skeleton. 

 Spicula, acuate, Jong, and slender. Spicula of inter- 

 stitial membranes same as those of dermal membrane. 

 Retentive spicula bidentate, equi-anchorate, few in 

 number. 



Colour. — White, in the dried state. 



Habitat. — Shetland ; deep water, Mr. Barlee. 



Examined. — In the dried state. 



This remarkable little sponge is in the form of a very 

 thin crust on the distal margin of the imperforated shell of 

 a small Terebratula caput-serpentis, Lam. It covers a space 



