BRITISH SPONGIADiE. 349 



The reticulated dermal membrane is very characteristic 

 in this species ; it is closely and compactly constructed ; 

 the sides of the network appear never to exceed a single 

 spiculum in length, and the areas are usually triangular or 

 quadrangular. The fibres of the skeleton are very stout, 

 and the areas of the network are usually very much elon- 

 gated. The tension spicula of both the dermal and inter- 

 stitial membranes are precisely the same as those of the 

 skeleton ; they are very abundant in the latter membrane. 

 The membranous gemmules were very abundant on the 

 interstitial membranes in the basal mass of the sponge, but 

 I did not detect any in the substance of the large cloacae. 



3. Desmacidon Peachii, Boioerbank. 



Sponge. Massive, sessile, compressed, somewhat fan- 

 shaped. Surface even but rough. Oscula simple, 

 dispersed. Pores inconspicuous. Dermal membrane 

 profusely spiculous ; tension spicula, acerate, varying 

 greatly in length, and of extreme tenuity, dispersed, 

 exceedingly numerous : retentive spicula, bihamate 

 simple, contort, and reversed; dispersed, occasionally 

 fasciculated, slender, very numerous. Skeleton. Coarse 

 and open in its texture, fibres stout ; spicula acuate, 

 large and rather long. Interstitial membranes pro- 

 fusely spiculous ; spicula the same as those of the 

 dermal membrane. 



Colour. Dried, light brown. 

 Habitat. Shetland, Mr. C. W. Peach. 

 Examined. In the dried state. 



I am indebted to my friend Mr. Peach for this species. 

 The only specimen I have seen is four inches in height, 

 three inches in its greatest breadth, rather exceeding an 

 inch in thickness at the base, and six or seven lines thick 

 at the distal margin ; it is compressed equably, and is ob- 

 liquely fan-shaped. Nearly the whole of the dermal mem- 



