BRITISH SPONGIADiE. 339 



principally Zoophytes, sometimes covering Lepralia, and at 

 others embracing the stalks of Plumularia. 



With a two inch lens the surface appears exceedingly 

 rugged and hispid. The oscula are simple, irregular per- 

 forations, varying much in size, and very numerous in com- 

 parison with the small size of the specimens. The biden- 

 tate equi-anchorate spicula of the dermal membrane are 

 irregularly dispersed, and are attached usually by the middle 

 of the bow; they are very minute and require from 600 to 

 700 linear power to distinctly determine their bidentate 

 character. 



37. IsomcTTA UNiFORMis, Bowsrbank. 



Sponge. Massive, sessile. Surface smooth. Oscula simple, 

 dispersed. Pores inconspicuous. Dermal membrane 

 abundantly spiculous : spicula acuate, dispersed, irre- 

 gular in size. Skeleton. Rete very irregular and 

 diffase ; primary lines multispieulous ; secondary lines 

 numerous, dispersed, and irregular, rarely more than 

 nnispiculous ; spicula acuate. Interstitial membranes. 

 Spiculous, same as those of the skeleton and dermis, 

 numerous, dispersed. 



Colour. — ^Dried, cream white. 



Habitat. — Guernsey, Rev. A. M. Norman. 



Examined. — In the dried state. 



The structure of this species is exceedingly simple. 

 The spicula are uniform in shape, and there is but one 

 form in all parts of the sponge. I received two small 

 specimens of the sponge from the Rev. A. M. Norman, 

 ■ who dredged them up off Guernsey. They were nearly of 

 the same size and form, half an inch in diameter, and about 

 two lines in thickness. The skeleton reticulations are very 

 irregular, and open in their structure ; the primary lines are 

 multispieulous, and the secondary ones numerous and irre- 

 gular, sometimes consisting of two or three spi<;ula, at others 



