BRITISH SPONGIAD^E. 187 



more than a single pore, and in that case the congregation 

 of the pores will become a very important specific character. 

 The existence of these areas and their mtermarginal cavities 

 approximates the dermal tissues of this sponge to those of 

 the corresponding parts of the genera Pachymatisma and 

 Geodia. When the sponge, as in Mr. Bean's specimen, 

 has not a mammillated surface, it may, in the dried con- 

 dition, be readily mistaken for Hymeniacidon pachy derma, 

 but the difference is at once obvious when reference is made 

 to the spicula. In the latter species they are not fusiform, 

 and their length is only as two to five of those of the 

 former species. 



I obtained at Hastings, at the latter end of March, 1863, 

 a still finer specimen of this sponge. It was two and a half 

 inches long, one and a half inches wide, and one inch thick. 

 As in the former cases there were no marks of an attach- 

 ment or base visible, and although a fully matured sponge, 

 there were no appearances of mammillation on its surface. 

 The oscula at one side were congregated to the amount of 

 twelve or fourteen, but in other parts they were irregularly 

 dispersed. From these circumstances, as compared with 

 those of the previously described specimens, it appears as if 

 there existed a great amount of variation in the external 

 characters of this species. 



An abundance of gemmules existed in this sponge, at- 

 tached to the parietes of the interstitial cavities. They 

 were globular, membranaceous, and aspiculous, semi- 

 transparent, and filled with distinct granular matter, and 

 they were of a light amber colour. The diameter of a 

 full sized one was ^ inch. In the living condition the 

 colour of the sponge was a light orange ; when dried, light 

 ochreous yellow, and in the latter state it is very hard and 

 solid. 



24. Hymeniacidon lingua, Bowerbank. 



Sponge. Massive, sessile ; surface somewhat corrugated. 

 Oscula simple, dispersed. Pores inconspicuous. Der- 



