HALICHONDBIA. 97 



slender. Skeleton diffuse and cavernous ; rete irre- 

 gular, rarely more than bispiculous ; spicula subcylin- 

 drical, acerate, shorter, and comparatively stouter than 

 those of the dermis. 



" Colour. In the dried state, dull brown. 



"Habitat. Durham coast, 20 to 35 fathoms; Rev. 

 A. M. Norman. 



" Examined. In the dried state. 



" This sponge occurs on the carapace of an aged spe- 

 cimen of a female Inachus Dorsetensis, on which, inter- 

 mixed with the sponge, there are small specimens of a 

 Balanus ; the surface, therefore, although smooth, is 

 very uneven. The oscula are minute and few in 

 number, and it required a lens of two inches' focus to 

 perceive them. The dermal membrane is abundantly 

 spiculous, and the spicula are dispersed without the 

 slightest approximation to order. They require the 

 application of a power of about 300 to render their 

 peculiarities of form distinct to the eye. They vary 

 to a considerable extent in diameter, although in 

 length they are nearly equal. The bidentate, equi- 

 anchorate, retentive spicula are very few in number, 

 but when present they are readily seen with a power 

 of about 100 linear ; the largest I measured was -^-g- 

 inch in length, and the smallest -gyg- inch. The biha- 

 mate spicula are of rather rare occurrence ; they are 

 smaller than the anchorate ones, and very slender, so 

 that it is difficult to detect them in situ amid the sar- 

 code with a less power than about 400 linear. Their 

 average length is y^-j inch. The structure of the 

 skeleton is diffuse and cavernous, and the rete is irre- 

 gular and rarely more than bispiculous. The termi- 

 nations of the fully developed skeleton spicula are a 



VOL. iv. 7 



