BRITISH SPONGIAD^. 153 



between the basal membrane and the dermal one, some- 

 times crossing each other, but frequently entirely isolated. 

 Their length very Httle exceeds that of a single spiculum. 



The internal defensive spicula are large and stout in their 

 proportions. They vary in length from ^th inch to yi^th 

 inch. In some of the dried specimens of the sponge the 

 points of the larger ones project beyond the surface, giving 

 it when viewed by direct light, with a power of 100 linear, 

 a slightly hispid appearance ; but as this evidently arises 

 from the contraction of the sponge in drying, it is not 

 probable that it would be apparent in the living state. 

 They are dispersed on the surface of the basal membrane, 

 at about equal distances from each other. Their spination 

 is very abundant to within a short distance of the apex, 

 which is smooth and acute, and at the base of the spiculum 

 they are abundant and very strongly produced. 



The retentive spicula are most abundant on the inner 

 surface of the basal membrane, but a few comparatively, are 

 dispersed in the interstitial tissues among the fasciculi of 

 the skeleton. The bidentate and tridentate equi-anchorate 

 spicula are stout and strong in their proportions, and the 

 dentse are more than usually widely spread. They are 

 dispersed equally on the surface of the basal membrane. 

 The simple bihamate spicula are about twice the length of 

 the anchorate ones, but their shafts are of extreme tenuity, 

 a portion of them are in groups, as if the bundles had been 

 partially broken up and dispersed, and occasionally isolated 

 spicula occur, but their usual mode of disposition is in 

 compact fasciculi, each consisting of a considerable number 

 of spicula, the hami being all coincident. This is the first 

 instance I have met with in which spicula of this form have 

 been collected in fasciculi. The thickness of this species 

 in the dried condition does not exceed ^^th inch ; in the 

 living state it may probably be 35th inch in thickness, but 

 although of such slight dimensions, the fully developed 

 condition of all its organs indicates an adult state of the 

 specimen. 



