BRITISH SPONGIAD.E. 191 



Colour. Dried, deep amber colour. 



Habitat. East Loch, Tarbet, Harris, N.B., 15 fathoms, 

 Captain F. W. L. Thomas, R.N. ; Strangford Lough, Pro- 

 fessor Dickie, Queen's College, Belfast. 



Examined. In the dried state. 



For the first specimen I received of this interesting species 

 I am indebted to the liberality and kindness of my friend 

 Captain Thomas, of the Hydrographical Survey. The 

 sponge covers nearly the whole of the gibbous valve of a 

 specimen of Pecten opercularis, and in the dried state it is 

 scarcely thicker than a sheet of stout writing-paper, and has 

 much the aspect of a layer of dried glue. The surface is 

 uniform and even. A few minute oscula were visible by 

 the aid of a lens of two inches focus, but no traces of the 

 pores could be detected. The interstitial membranes are 

 profusely furnished with skeleton spicula, and when seen 

 edgeways look very like large long sinuous fasciculi of spi- 

 cula. The tension spicula are few in number. The sarcode 

 is abundant, and of a deep amber colour. The prominent 

 feature in this sponge is the striking form and mode of ar- 

 rangement of the retentive spicula, and especially so of the 

 dentato-palmate inequi-anchorate ones, which in this sponge 

 are developed in a more complete and perfect form than I 

 have hitherto seen ; they are in great abundance, and nearly 

 the whole of them are congregated in beautiful rosette- 

 shaped groups, the small or proximal ends of the spicula 

 being clustered together in the centre, while the shafts and 

 distal palms radiate at angles of about 45 degrees from the 

 membrane on which they are seated, the number of spicula 

 in each group varying from six or seven to seventeen or 

 twenty, and sometimes more. On some parts of the mem- 

 branous tissues they are more numerous than on others, and 

 in one case I counted fifteen groups in a circle of 33rd of an 

 inch in diameter. Occasionally a solitary spiculum of this 

 form may be seen on the membrane, but these single spicula 

 are comparatively few in number. The bidentate inequi- 

 anchorate spicula are much fewer in number than the den- 



