BRITISH SPONGIADjE. 125 



pustulous. Oscula simple, dispersed. Pores incon- 

 spicuous. Dermal membrane spiculous ; spicula 

 acerate, long, and slender, dispersed, numerous ; 

 retentive spicula equianchorate, tridentate, minute, 

 short and stout, rather numerous. Skeleton : columns 

 diffuse, long, and very irregular ; spicula acerate, 

 rather long and slender. External defensive spicula 

 basally spined, attenuato-acuate or spinulate, long and 

 rather slender, usually curved near the base. Internal 

 defensive spicula entirely spined, attenuato-acuate, 

 short ; spines numerous and strongly produced. In- 

 terstitial membranes spiculous ; tension and retentive 

 spicula same as those of the dermal membrane, both 

 numerous. 



Colour. Dried, brown with a tint of yellow. 

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

 Examined. In the dried state. 



The specimen in course of description rather exceeds an 

 inch and a quarter in length. It has entirely enveloped, 

 apparently, the stem of a branching horny zoophyte ; one 

 portion of it is nearly cylindrical, with a diameter of rather 

 more than two lines ; the other is about the same thickness, 

 but flat, and is rather more than five lines wide. 



The general aspect of this sponge is so unlike that of 

 other species of Microciona that it is very likely to deceive 

 a hasty observer, and the confusion of its internal structures 

 arising from their true bases being on the cylindrical sur- 

 faces of the zoophyte or fucus whence they spring, instead 

 of on an expanded plane, increases the difficulties of identi- 

 fication ; but a close examination of its structure in detail 

 irresistibly leads to the conclusion that it is truly a Micro- 

 ciona. 



The depressed pustulous character of the surface in the 

 dried specimen is, with the aid of a lens of an inch focus, 

 very characteristic, but it is probable that it is not apparent 

 in the living sponge. Sometimes the pustules appear to be 

 furnished with a closed osculum, but other oscula are seen 



