BRITISH SPONGIAD^. 267 



in length, half an inch in height, and rather less than a 

 quarter of an inch thick at the lower edge, and gradually 

 becomes thinner towards the upper edge ; one end is de- 

 cidedly a fractured one, the other appears to be a natural 

 termination ; the characters, therefore, of form and attach- 

 ment require confirmation from more perfect specimens. 

 The oscula are also rather indistinctly characterised, as ex- 

 hibited by this mutilated specimen ; they are simple, small, 

 and irregular in form, and a few only are really conspicuous 

 without the aid of a lens. The dermal membrane is pel- 

 lucid, but the inner surface is abundantly covered with the 

 dark-coloured sarcode. 



The terminally spined sub-fusiformi-cylindrical spicula are 

 disposed in irregular fasciculi, and from the indistinctness of 

 the tissues arising from the dark-coloured sarcode, they may 

 be readily mistaken for portions of the network of the skeleton 

 immediately beneath. The palmato- and dentato-inequi- 

 anchorate and inequi-bipocillated spicula are irregularly 

 dispersed in both the dermal and interstitial membranes ; 

 the former two did not appear in any instance to be at- 

 tached to the membranes by the smaller termination, as 

 might have been expected from their form, but in every 

 instance observed, the attachment was at about the middle 

 of the bow of the spiculum. It was with much difficulty 

 that I found the inequi-bipocillated spicula in situ on the 

 interstitial membranes ; the larger end appeared to project 

 slightly above the surface of the sarcode, but the line of 

 projection was not in any one of the three I observed at 

 right angles to the plane of the membrane. I did not 

 detect them in situ in the dermal membrane, but I have no 

 doubt that they belong to it as well as to the interstitial 

 ones. This and H. Hyndmani are the only British sponges 

 in which I have yet found this very minute and singular 

 form of spiculum, which requires a power of 400 linear to 

 render it distinctly visible. The dimensions of an averaged 

 sized one which I measured was length st^end inch ; diameter 

 of largest termination jn^nd inch; diameter of smallest 

 termination s^rd inch, while the anchorate spicula, although 

 small of their kind, measured in length jjjth inch. 



