BRITISH SPONGIAD^. 287 



The acerate spicula of the skeleton are short in com- 

 parison with many other species having the same form ; 

 the tension spicula of the interstitial membranes are very 

 little inferior in length to the skeleton spicula, but much 

 more slender. The only species of Halichondria with 

 which this sponge is likely to be confounded is IT. caduca, 

 but the difference in the length of their skeleton spicula 

 readily serves to distinguish them, those of H. inconspicua 

 being little more than half the length of those of H. 

 caduca. I am indebted to my kind friend Mrs. Brett, of 

 Tenby, for this new species. It was gathered between high- 

 and low-water marks on the northern side of St. Katherine's 

 Rock, at Tenby, and I am informed was nearly of the 

 same colour when alive as it is in the dried state, and that 

 while drying it emitted a smell similar to heated vinegar. 



6. Halichondria incerta, Bowerbank. 



Sponge. Sessile, coating. Surface rough and uneven. 

 Oscula simple, dispersed, numerous. Pores incon- 

 spicuous. Dermal membrane abundantly spiculous ; 

 spicula acerate, rather slender, dispersed, closely felted 

 together. Skeleton irregular, rete slender, very in- 

 distinct, spicula acerate, as long, but stouter than 

 those of the dermal membrane. Interstitial mem- 

 branes, tension spicula very abundant, same as those 

 of the dermal membranes, irregularly dispersed. 



Colour. — Dried, sulphur yellow. 



Habitat. — Guernsey, Rev. A. M. Norman. 



Examined. — In the dried state. 



This sponge entirely coats a Balanus about an inch in 

 height, but does not attain a greater thickness than a line, 

 in any part. The dermal membrane is remarkably crowded 

 with spicula, they cross each other in every possible direc- 

 tion, and present the appearance of having been felted 

 together, and this crowding of the spicula appears to obtain 



