1SODICTYA. 137 



diameter, rather evenly dispersed ; retentive spicula 

 bidentate, equi-anchorate, minute, few in number. 

 Skeleton rather irregular in structure ; primary 

 lines of rete uni- or bispiculous, rarely trispiculous ; 

 spicula acuate, comparatively large, uniform in size ; 

 secondary lines uni- or rarely bispiculous ; tension 

 spicula acuate, slender, few in number ; retentive 

 spicula bidentate, equi-anchorate, frequently rather 

 more numerously dispersed in the interstitial mem- 

 branes than in the dermal one. Sarcode rather abun- 

 dant. 



" Colour. In the dried state, dark grey. 



"Habitat. Roundstone Bay, Ireland; Rev. A. M. 

 Norman. 



" Examined. In the dried state. 



" I received two small specimens of this sponge, deeply 

 embedded amid the short branches of two specimens 

 of Nullipora polymorpha. To the unassisted eye their 

 surfaces appeared smooth and even, but when sections 

 at right angles to the surface were examined in Canada 

 balsam it was seen that they were abundantly hispid, 

 the hispidation being produced by the prolongation and 

 projection of the distal terminations of the primary 

 fibres of the skeleton. These defensive organs most 

 frequently consist of two or three spicula, which diverge 

 slightly from each other, and are frequently projected 

 more than the length of a single spiculum beyond the 

 surface of the dermal membrane. This mode of arma- 

 ture is very characteristic of the species. The dermal 

 membrane is abundantly supplied with tension spicula^ 

 which are irregularly but rather evenly dispersed, so 

 that they sometimes appear to simulate a widely-con- 

 structed reticulation. They are about the same length 



