60 BEITISH SPONGIADJ!, 



" Colour. — In the dried state, dark amber-brown. 



" Habitat. — Birterbuy Bay, Ireland ; Eev. A. M. 

 Norman. 



" Examined. — In the dried state. 



" This sponge is spread very thinly on the inner sur- 

 face of a fragment of a shell of Pecten maximus. It 

 is one inch in length, and its greatest width does not 

 exceed half an inch. "When a portion of it mounted 

 in Canada balsam is examined with a power of 300 

 linear it presents a very singular appearance. When 

 the thickness of the sponge does not exceed about half 

 the length of the internal defensive spicula, projected 

 at right angles from the basal membrane through the 

 dermal one, the surface appears minutely hispid, and 

 the dermal membrane in a very pellucid state is dis- 

 tinctly to be seen with numerous minute and slender 

 bihamate, retentive spicula dispersed on its inner sur- 

 face. When the thickness of the sponge exceeds the 

 length of the internal defensive spicula the dermal 

 surface then appears smooth, and the membrane, abun- 

 dantly furnished with dark, amber-coloured sarcode, 

 becomes very nearly opaque, and the structures be- 

 neath are entirely obscured. In this condition its 

 greatest thickness appears to be about twice the 

 length of the internal defensive spicula, which mea- 

 sured -sk^ iiich in length ; so that its greatest thick- 

 ness does not appear to exceed about pfy inch. The 

 bihamate spicula of the dermal membrane are rather 

 abundant, but very minute and slender, and they 

 require a power of not less than 400 linear to show 

 them distinctly as they lie in situ. The skeleton also 

 presents very anomalous characters. The spicula of 

 which it is composed are like those of the system of 



