302 A MONOGRAPH OF THE 



The skeleton spicula are rather slender in their pro- 

 portions ; one of the largest and best developed specimens 

 measured x^th inch in length. 



The length of the spicula of this sponge is very nearly 

 the same as that of /. pallida, cinerea and indistinda, but 

 it may be readily distinguished from these species by its 

 external characters, and especially so by its prominent 

 hispidation. 



I have dedicated this species to the Rev. Walter Gregor, 

 late of Macduff, now of Aberdeen, an able and ardent 

 working naturalist, to whom I am indebted for the use of 

 many interesting northern species during the progress of 

 my work. 



19. IsoDicrYA FALLAX, Bowerbank. 



Sponge. Massive, sessile. Surface even, smooth; fur- 

 nished irregularly with fistular projections, variable in 

 size and form; parietes thin. Oscula terminating 

 large fistulse. Pores conspicuous, numerous. Der- 

 mal membrane thin and pellucid, furnished with a 

 unispicular network, smooth ; spicula same as those 

 of the skeleton ; tension spicula acerate, very slender; 

 few in number ; and tricurvate acerate, minute and 

 very slender, rather numerous. Skeleton. Diffuse 

 and very irregular ; primary and secondary hnes 

 scarcely to be distinguished, mostly unispiculous ; 

 spicula acerate, rather long. Interstitial membranes. 

 Tension spicula same as those of the dermal mem- 

 branes. 



Colour. — ^Dried, hght gray. 



Habitat. — Off Saints' Bay, Guernsey, Rev. A. M. 

 Norman. 



Examined. — In the dried state. 



I received the specimen described above, in company 



