80 BRITISH SPOXGIADJi. 



" Examined. Fresh from the sea. 



" The external aspect of this sponge is so like that of 

 Battersbyia BucMandi, being of the same dark colour, 

 and of a similar degree of solidity, that it may readily be 

 mistaken for that sponge by a superficial observer, but 

 the slightest attempt at a microscopical examination of 

 its structural characters will at once distinguish it from 

 that species. The oscula were all closed, but the 

 position of several of them, by the aid of a lens of two 

 inches' focus, was apparent from the small depressed 

 areas on the dermal surface. The characters of the 

 dermal membrane are not readily to be determined, as it 

 is closely adherent to the dense complicated mass of the 

 spicula of the skeleton beneath it, but in the few spots 

 where its structure was apparent I could not detect 

 the slightest traces of characteristic dermal spicula or 

 of any especial arrangement of the forms common to 

 the whole mass of the sponge. 



" The skeleton spicula are closely felted together 

 without the slightest approximation to arrangement at 

 any part of the sponge, and it is only at a few internal 

 cavities that the interstitial membranes are visible, and 

 they, like the dermal one, are aspiculous. The colour 

 of the sarcode is very nearly black at both its upper 

 and basal surfaces when the sponge is fresh and in a wet 

 condition. "When a section at right angles to the sur- 

 face is mounted in Canada balsam and viewed by trans- 

 mitted light with a power of about 100 linear, the 

 colour and opacity is seen to gradually decrease until 

 the internal portions of the structures are pale in colour 

 and transparent. The greater portion of the skeleton 

 spicula are purely acuate in form, but a few of them 

 exhibit more or less of a tendency to spinulation. 



