BRITISH SPONGIAD.E. 305 



closely resembling the multispiculous keratose fibres of a 

 Desmacidon, running irregularly amidst the other portions 

 of the skeleton, in directions more or less parallel to the 

 outer surfaces of the sponge, but without appearing to 

 interfere with, or subordinate to its stronger parts, the 

 original isodictyal portions of the skeleton. These pecu- 

 liarities of structure strongly induce me to believe that the 

 sponge should form the type of a new genus ; but for the 

 present, and until we obtain further knowledge of it, it 

 will be as well to allow it to be considered as an Isodictya. 



The retentive spicula are very minute, and apparently 

 very few in number. In their form they very nearly 

 approach that of a semicircle. 



The Rev. A. M. Norman found this species very 

 abundant about thirty miles east of the Outer Skerries, 

 Shetland. 



21. Isodictya pocillum, Bowerbank. 



Sponge. Cup-shaped, pedicelled. Surface irregular, ru- 

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

 spicuous. Dermal membrane aspiculous. Skeleton. 

 Irregular and indistinct in its structure ; primary lines 

 multispiculous ; secondary lines also frequently multi- 

 spiculous, or confusedly unispiculous ; spicula acerate, 

 stout. External defensive spicula attenuato-acuate, 

 slender, and very long. 



Colour. Nut-brown, in the dried state. 

 Habitat. Off Saints' Bay, Guernsey, Rev. A. M. Nor- 

 man. 



Examined. In the dried state. 



I have seen but one specimen of this sponge. It is 

 irregularly cup-shaped, and does not exceed an inch 

 in height. It is elevated on a short stout pedestal, 

 about a quarter of an inch in length, and its greatest dia- 

 meter is three quarters of an inch ; its thickness does not 



20 



