296 A MONOGRAPH OF THE 



and the structural characters of the sponge exceedingly 



simple. 



The only species with which, in the dried state, it might 

 be confounded is I. indistincta, but the rete is very 

 much more regular than in that species, nor are the pores 

 congregated as in /. indistincta. The hispid condition of 

 the dermal membrane also strongly marks the difference 

 between them. 



15. Isodictya jugosa, Bowerbank. 



Sponge. Sessile, coating. Surface uneven, ridged, and 

 furrowed, minutely hispid. Oscula simple, dispersed. 

 Pores inconspicuous. Dermal membrane pellucid, 

 furnished rather abundantly with simple and contort 

 bihamate spicula. Skeleton. Somewhat irregular; 

 spicula acerate, rather long and stout. Interstitial 

 membranes ; furnished rather sparingly with simple 

 and contort bihamate spicula. 



Colour. Dried, light fawn-yellow. 

 Habitat. Shetland, Rev. A. M. Norman. 

 Examined. In the dried state. 



This little sponge is parasitical on a small group of 

 vermetus. It is nine lines in length, and about two lines 

 in thickness. When viewed with a lens of two inches focus, 

 the surface is seen to be full of prominent ridges and deep 

 furrows, running in tortuous directions. The hispidation 

 is comparatively bold and strong. It is produced by the 

 projection of the distal terminations of the primary radial 

 lines of the skeleton. The oscula are comparatively large 

 and numerous, especially at the distal end of the sponge. 

 The bihamate spicula of the dermal membrane are abun- 

 dant, but they are not visible without the aid of Canada 

 balsam. 



A dried specimen of this sponge may be readily mis- 

 taken for a specimen of Isodictya indefinitus, the structural 



