BRITISH SPONGIADyE. 165 



Habitat. Forty miles east Outer Skerries, Shetland, 

 Rev. A. M. Norman. 



Examined. In the dried state. 



I am indebted to my indefatigable friend the Rev. A. M. 

 Norman for my knowledge of this species ; he obtained it 

 by dredging. The specimen is nearly two inches in length 

 and breadth, and about a line and a half in thickness. 

 The oscula are nearly uniform in size, none exceeding about 

 a line and a half in diameter, and they are elevated above 

 the surface about one third or half a line. The spicula of 

 the dermal membrane are the same as those of the skeleton ; 

 and among them the bi- and tridentate equi-anchorate 

 retentive spicula, are abundantly dispersed, and compara- 

 tively they are very stout and large ; no internal defensive 

 attenuato-clavate spicula appear among them. The skeleton 

 spicula are exceedingly abundant, and are very closely 

 matted together, and occasionally they are sub-fasciculate. 

 The internal defensive spicula frequently exceed the skeleton 

 ones in length. The extremely long ones appear all of 

 them to spring from the basal membrane of the sponge, 

 while the shorter varieties are situated on the interstitial 

 membranes. The spination of these spicula is exceedingly 

 abundant especially at their club-shaped bases. These 

 spicula very closely resemble the corresponding organs in 

 Hymeniacidon clavigcra, but there is no difficulty in dis- 

 criminating the species, as their skeleton spicula are dis- 

 tinctly different in form. 



10. Hymeniacidon membrana, Boicerbank. 



Sponge. Coating, thin ; surface smooth and even. Oscula 

 dispersed, simple or slightly elevated ; few in number, 

 and rather large. Pores inconspicuous. Dermal 

 membrane abundantly spiculous. Spicula same as 

 those of the skeleton. Skeleton. Spicula acerate, 

 small, but not long in proportion ; numerous ; very 

 rarely acuate. 



