268 PLATE LXXXII. 



and its anatomical details it is in perfect accordance 

 with the type-specimen, 



DESMACIDON CAVERNULA, BowerbanA. 

 Plate LXXXII. 



Sponge massive, irregular ; interior cavernous, with 

 large external orifices ; surface uneven and very rugged. 

 Oscula simple ; few external, the greater part internal. 

 Pores inconspicuous. Dermal membrane abundantly 

 spiculous ; tension spicula either dispersed or forming 

 an irregular reticulation, acuate, nearly as large as those 

 of the skeleton; retentive spicula contort, bihamate, 

 rather stout, few in number. Skeleton fibre stout and 

 compact ; spicula fusiformi-acuate. Interstitial mem- 

 branes spiculous ; tension and retentive spicula same 

 as those of the dermal membrane, dispersed ; retentive 

 spicula few in number. 



Colour. In the dried state, dark brown. 



Habitat. Haaf banks, Shetland, Mr. Humphreys. 



Examined. In the dried state. 



I received this sponge with other species from the 

 fishermen at the Haaf banks, Shetland, through their 

 agent Mr. Humphreys many years since, and it escaped 

 my observation until very lately, when I found it among 

 my numerous duplicates. Its form is that of an irre- 

 gularly compressed mass. Its greatest breadth is one 

 inch and a half and its average thickness about three 

 fourths of an inch. There is no appearance of a basal 

 attachment. The interior is one large irregular cavern 

 into which there are six openings, one of them being 

 eight lines in breadth and three in height. The 

 cavernous interior is covered with a dermal membrane 

 like that of the exterior surface, which is inflected 

 through all the great openings into the interior, and 

 its surface characters within the sponge are precisely 

 the same as those of the external dermal membrane-. 



