BRITISH SPONGIADiE. 279 



has not the slightest trace of the peculiar reticulated ap- 

 pearance of that species, when examined with a lens of two 

 inches focus. The specimens sent to me by Mr. Bean 

 were thoroughly washed, and in that state they were of a 

 light yellow colour, very fragile, readily compressible, and 

 soft to the touch. I subsequently received two small 

 specimens from Mr. Peach, which appeared to have been 

 dried in the state in which they came from the sea, and 

 these were of a nut-brown colour, well furnished with 

 sarcode, and were consequently considerably more rigid and 

 firm to the touch. The reticulations of the skeleton are 

 very distinct and regular ; they are rarely wider or longer 

 than the length of a single spiculum ; the primary lines of 

 the skeleton are most frequently unispicular, and the 

 secondary ones, I believe, always so. The skeleton spicula 

 are regularly acerate, and are short and stout in their pro- 

 portions. A full-sized one measured — th inch long. The 

 dermal membrane in all the specimens I have examined 

 was in so dilapidated a condition as scarcely to allow of my 

 speaking with certainty on the subject of the specific cha- 

 racters to be derived from it. On the board to which four 

 specimens are attached, in the Johnstonian collection in 

 the British Museum, and which are designated Halichon- 

 dria cinerea, there are two on one piece of card ; the 

 smaller one is identical with our I. per mollis. The mark 

 on the card is W. 



4. IsoDicTYA siMULO, Bowerbank. 



Sponge. Coating. Surface smooth, or rarely minutely 

 hispid. Oscula simple, dispersed, large. Pores incon- 

 spicuous. Dermal membrane pellucid, spiculous ; 

 spicula acerate, slender, dispersed ; shorter than those 

 of the skeleton, moderately abundant. Skeleton : 

 primary lines bi- or trispiculous ; secondary lines uni- 

 spiculous; spicula sub-fusiformi acerate, short, and 

 rather stout. Interstitial membranes, tension spicula, 

 same as those of the dermal membrane ; few in num- 



