86 



PLATE XXXIII. 



colour. In fig. 19 it will be observed that the oscula 

 are very slightly elevated above the dermal surface, 

 while in the sponge represented by fig. 20 the entire 

 surface is crowded with excurrent cloacae. In fact the 

 species appears to be almost as variable in form as that 

 of Halichondria panicea. 



Fig. 21. — One of the skeleton spicula. X 150 

 linear. 



Fig. 22.- — An acuate, slender spiculum, from the 

 interstitial membranes. X 150 linear. 



Mr. C. Stewart has also found this species rather 

 thinly coating small boulders of stone at Plymouth. 



