BRITISH SPONGIAD^E. 249 



and in these I did not succeed in detecting any tension or 

 other spicula. 



14. Halichondria incrustans, Johnston. 



Halichondria saburrata, Johnston. 

 panicea, Grant. 



Sponge. Sessile, massive ; surface uneven. Oscula dis- 

 persed, large, simple; sometimes more or less elevated. 

 Pores inconspicuous. Dermal membrane thin, pellucid, 

 furnished abundantly with large flat fasciculi of cylin- 

 drical mucronate spicula, and with, bihamate simple, 

 reversed, and contort retentive spicula, and also with 

 bi-dentate equi-anchorate spicula. Skeleton. Acuate 

 or subfusiformi-acuate, entirely spined, stout and rather 

 short. 



Colour. Buff, yellow or orange colour when alive. 



Localities. Frith of Forth, Dr. Grant. Hebrides, Ork- 

 neys and Shetland, Captain Thomas. Welsh and Irish 

 Coasts, Channel Islands, Hastings, &c, J. S. Bovverbank. 



Examined. Alive. 



This is a very remarkable sponge, and will well repay a 

 careful microscopical examination. The spicula of the 

 skeleton are acuate, and occasionally sub-spinulate, more 

 perhaps from a profusion of spines at the base than from 

 enlargement of that extremity, and all parts of the spiculuui 

 are abundantly spinous. The dermal membrane, which can 

 be best obtained at the sides and near the base of the 

 sponge, is thin and transparent, and most profusely fur- 

 nished with large and flattened bundles of cylindrical spicula 

 without spines, but sometimes having their terminations 

 more or less acute instead of hemispherical. In very young 

 specimens the bihamate and anchorate spicula are frequently 

 not to be detected, and the flat fasciculi of spicula on the 

 dermal membrane are sometimes quite detached from each 



