BRITISH SPONGIAD^. 265 



regards each other, are also corymbose. The inequality in 

 the size of the flukes of the inequi-anchorate spicula of the 

 dermal membrane is quite as great as those in the similar 

 membrane of Halichondria lingua, but they are very much 

 fewer in number, and very minute ; and I could not de- 

 tect any such symmetrical arrangement of them as exists 

 in H. lingua. The internal defensive spicula are com- 

 paratively few in number ; they may be readily distinguished 

 from those of the skeleton, from being not more than about 

 half their length, and from being spinous from base to apex, 

 while the distal half of those of the skeleton is without 

 spines. The membranous interstitial structure is abun- 

 dantly furnished with very minute bidentate inequi-anchorate 

 spicula, which are not readily to be seen in situ, until a 

 minute portion of the sponge has been mounted in Canada 

 balsam, they are then seen most frequently attached to the 

 membrane by the middle of the back of the bow of the 

 spiculum; they are disposed without order, and are so 

 minute as to require a linear power of from 600 to 700, to 

 render them visible. The varieties in the form of the bi- 

 pocillated spicula is very great, scarcely any two being 

 precisely ahke in the extent or mode of their develop- 

 ment. 



I obtained a specimen of this sponge at Hastings, thinly 

 coating the two valves of a specimen of Pecten opercular is. 

 In this form, it very closely resembles a Hymeniacidon in 

 its structure, exhibiting very indistinct traces of reticulated 

 skeleton ; but in every other organic structure it agreed 

 perfectly with the Strangford Lough specimens. It was 

 taken in trawling at the Diamond Fishery Ground, off 

 Hastings, in February, 1862. Its colour was dark purple. 

 I have also received two specimens dredged in the Moray 

 Frith, by the Rev. Walter Gregor, of Macduff, six miles off 

 shore, in forty-two fathoms, one of these specimens is 

 parasitical on a small branching Fucus, covering it com- 

 pletely, and thus in its general contour closely resembles a 

 small Dictyocylindrus. The other coats all parts of a small 

 Zoophyte, confusedly matted together. The external form 

 appears to be subject to very great variations dependent 



