252 A MONOGRAPH OF THE 



Habitat. Dredged off St. Martin's Point, Guernsey, 

 Rev. A. M. Norman. 



Examined. In the dried state. 



I received eight specimens of this sponge from the Rev. 

 A. M. Norman. None of them exceeded two inches in 

 length or an inch in height. One only had tuberculous 

 elevations on the surface, each terminated bv an osculum. 

 In the other specimens the oscula were dispersed irregularly 

 on the surface without elevation, The hispidation of the 

 surface is so minute, that it is only when mounted in 

 Canada balsam that it is apparent ; it is produced by 

 radiating fasciculi of the smooth acuate spicula of the dermal 

 membrane, which are projected for about half their length 

 through that organ ; sometimes they spring from the 

 skeleton reticulation beneath, but very often they are uncon- 

 nected with it, and are based on the interstitial membranes 

 only. The pores are large, and comparatively few in num- 

 ber. The skeleton is very compactly constructed, the rete 

 often having as many as four or five spicula closely 

 cemented together, and the areas are as frequently trian- 

 gular as they are quadrangular. The interstitial membranes 

 are very translucent, and the sarcode is by no means abun- 

 dant. The tension spicula are of rather rare occurrence, 

 and the retentive spicula do not appear to be nearly so 

 numerous as they are in the dermal membrane. 



16. Halichondria irregularis, Bowerbank. 



Sponge. Massive, sessile ; surface uneven, rugose. Oscula 

 simple, dispersed, small. Dermal membrane pellucid, 

 abundantly spiculous ; spicula sub-fusiformi acerate, 

 large, fasciculated and sub-reticulate ; and bidentate 

 angulated equi-anchorate retentive spicula abundantly 

 minute. Skeleton irregular and indistinctly reticulate. 

 Spicula attenuato-acuate, basally and medially spined, 

 stout and rather long. Internal defensive spicula 

 attenuato-acuate, entirely spined, short and strong. 



