BRITISH SPONGIAD^. 99 



the sponge, and these are frequently terminated with a 

 fasciculus of long, slender, acerate, defensive spicula. The 

 marginal fringe of the sponge is formed by a continuation 

 of the central stratum of large spinulate spicula slightly 

 beyond the soHd margin of the sponge, and by the addition 

 of numerous long, acerate, defensive spicula. The inter- 

 stitial membranes are thickly covered with sarcode, in 

 which there are numerous minute granulated vesicles. 



Since the above description was written I have received 

 two specimens for examination from the Rev. A. M. 

 Norman, who dredged them at Shetland in 1863. One 

 was nine lines and the other seven lines in diameter and 

 each had a small pebble imbedded in its centre, and in 

 every other respect they closely resembled the specimens 

 described. Two other specimens, dredged in the same 

 locality, in 1864, were sent to me by my friend Mr. C. W. 

 Peach ; the diameter of one specimen was one inch, and of 

 the other seven lines. The central pebble in neither of 

 these specimens was visible but its presence was indicated 

 by a slight projection near the middle of the concave sur- 

 face of each, and on probing these spots with a sharp 

 needle their impenetrability gave assurance of its presence. 

 From the size of Mr. Peach's largest specimen being the 

 same as the large one from Mr. Barlee, it is probable that 

 the greatest diameter of this species rarely exceeds one 

 inch. 



