BRITISH SPONGIADiE. 377 



defensive spicula, same as those of the skeleton ; pro- 

 jected upward at angles from 12 to 45 degrees to 

 the axes of the primary fibres ; secondary fibres not 

 containing spicula ; defensive spicnla usually single, 

 projected upward at about right angles to the fibres 

 on which they are based. Spicnla fusiformi-acuate, 

 short and stout. Interstitial membranes spiculous ; 

 spicula slender, sub-fusiformi-acuate and tricurvate 

 acerate, very slender. 



Colour. Alive, dark blood-red. 



Habitat." Frith of Forth, Dr. Grant; Island of 

 Ireland's Eye, off the Dublin Coast, Wm. Thompson, Esq." 

 St. Katherine's Rock, Tenby, J. S. Bowerbank ; Bantry 

 Bay, Falmouth, and Jersey, Rev. A. M. Norman. 



Examined. In the living state. 



This species does not appear to attain a considerable 

 size. I have never seen specimens exceeding three inches 

 in diameter, and half an inch in thickness, and it is fre- 

 quently found not more than two or three lines in thickness, 

 smoothly and evenly coating the rock on which it is based. 

 In the living condition the hispidation is rarely to be 

 detected without the dermal membranes, the terminal 

 fasciculi of the primary radiating lines of the skeleton 

 having their apices immediately beneath the membrane, but 

 in other cases they distinctly penetrate and pass through 

 that organ. The oscula are very characteristic of the 

 species, and there is a considerable amount of uniformity 

 in their diameters, and in the mode of their disposition. 

 The tricurvate tension spicula of the dermal and interstitial 

 membranes are rather unusual in their form, the central 

 curve is greatly produced, while the terminal curves are 

 sometimes scarcely apparent. These spicnla are rather 

 numerous and variable in size. The structure of the 

 skeleton is very remarkable. The primary lines of fibre 

 are composed of stout fusiformi-acuate spicula and keratode 

 irregularly cemented together, and from the sides of this 

 fibre numerous spicula similar in form and size to the im- 



