126 DR. J. S. BOWERBANK ON THE SPONGIAD.E. [Feb. 6, 



Hymeniacidon pulvinattjs, Bowerbank. 



Sponge sessile, massive. Surface smooth, tuberculated. Oscula 

 simple, numerous, dispersed, small. Pores inconspicuous. Dermal 

 membrane thin, abundantly spiculous ; spicula closely and irregu- 

 larly felted together, fusiformi-spinulate, as large as those of the ske- 

 leton. Skeleton arranged in large, thick, sinuous, irregularly formed 

 plates of skeleton- tissue, running in various angles towards the der- 

 mal surface, separated from each other by very large interstitial 

 cavities disposed in the same direction as the skeleton-plates ; spicula 

 fusiformi-spinulate or subclavate. 



Colour in the dried state ochreous yellow. 



Hab. Calibert Quay, twenty miles due east of Belize, in 8 feet 

 water (Mr. Dyson). 



Examined in the dried state. 



This sponge is, I believe, the largest recent species known to na- 

 turalists. Two specimens of it were found by Mr. Dyson at Calibert 

 Quay, in the neighbourhood of which he was collecting speci- 

 mens of natural history. He told me that the summit of the 

 largest specimen was just below the surface of the water, and that 

 he passed one of the oars down by the side of the sponge and found 

 that it was 8 feet in height, and that they chiselled off the top of 

 the sponge with the oars and cut it into three pieces for the conve- 

 nience of packing it. What the diameter of this enormous mass was in 

 the living state he did not tell me ; but in its present dried condition 

 its greatest diameter is 34 inches, and its lesser one 29 inches. The 

 second specimen, which appears to have been very little inferior iu 

 size, has a diameter of 27 by 21 inches. The surface is smooth but 

 abundantly tuberculated ; the tubercles are small and depressed, 

 rarely exceeding an inch in diameter, and are less than an inch in 

 height. The oscula are numerous and small, rarely exceeding 2 

 lines in diameter ; they are simple orifices of a circular or oval form. 

 The dermal membrane is crowded with spicula so thickly felted 

 together that their forms can scarcely be determined even when 

 mounted in Canada balsam, excepting at the thin edge of the speci- 

 men ; if there be any difference between them and those of the 

 skeleton, it is that they are rather less in size. 



The interior mass of the sponge is formed of thick, sinuous, irre- 

 gularly shaped plates of skeleton- structure, all more or less disposed 

 in the direction of the external surface, where they expand beneath 

 the dermal membrane ; and over these expansions the pores are situ- 

 ated. The plates of skeleton-tissue are separated from each other by 

 very large interstitial spaces, each one being lined by an interstitial 

 membrane. These large spaces accompany the skeleton-plates in 

 their progress to the dermal surface ; and immediately above their 

 terminations the oscula are found, varying in number from one to 

 two or three. 



The structures of the skeleton-tissues are quite in accordance with 

 those of numerous other species of Hymeniacidon ; for it must be 

 remembered that, however large or small a sponge may be, the ana- 



