BRITISH SP0NGIAD.E. 209 



a power of 660 linear, it presented a remarkably imperforate 

 appearance, the pores being rarely visible. The dermal 

 membrane is not a mere film, but has comparatively a con- 

 siderable amount of thickness, and is thickly coated in- 

 ternally with spinulate spicula, closely felted, as it were, 

 together, interspersed with which there are numerous minute 

 ones of the same form. 



The spicula of the interstitial membranes are of the same 

 form as those of the dermal one, but somewhat stouter and 

 shorter in their proportions, and they are not quite so 

 numerous, although very abundant, and the minute spinulate 

 ones are not by any means so abundant. The sarcode 

 presents the appearance of a firm amber coloured jelly, of 

 uniform consistence, when viewed with a power of 400 linear. 



The specimen sent to me by my friend Mr. Bean, was 

 labelled Halichondria sulphur ea, and I have therefore 

 adopted his very appropriate name, as in its dried condition 

 it causes the stone which- it coats to appear as if it had 

 been washed over with a thick infusion of milk of sulphur. 



The Rev. A. M. Norman subsequently sent me a speci- 

 men of this species from Guernsey, which covered part of 

 the shell of an oyster to about the same degree of thickness 

 as that of the type specimen, with which it also agreed in 

 every other respect. 



33. Hymeniacidon subclavata, Bowerbank. 



Sponge. Coating. Surface even, smooth. Oscula simple, 

 dispersed. Pores inconspicuous. Dermal membrane 

 abundantly spiculous ; spicula sub-fasciculated, fusi- 

 formi-sub-clavate, rarely acuate, slender and frequently 

 flexuous, about as long as those of the skeleton. Skele- 

 ton : spicula fusiformi-sub-clavate, rarely purely acuate, 

 stout, and moderately long. Retentive spicula, con- 

 tort bihamate, large and slender, very numerous , and 

 bidentate inequi-anchorate, very minute ; and rarely 

 dentato-palmate inequi-anchorate. 



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