ISODICTYA. 125 



still further complicated by the intermixture of the 

 long and slender tension spicula. The same compli- 

 cation of characters exists in the skeleton structures 

 by the abundant presence of the long slender tension 

 spicula on the interstitial membranes ; so that although 

 but one form of spiculuin, that of the f usif ormi-acerate, 

 stout and slender, prevails in this sponge, the pecu- 

 liarities of their intermixture render this species a 

 specially perplexing one for specific determination." 



24. ISODICTYA DENSA, Bow., n, 292 ; in, 355, PI. L, 

 figs. 57. 



25. ISODICTYA G-REGORII, Bow., n, 301 ; in, PL L, 



figs. 1517. 



26. ISODICTYA PALLIDA, Bow., n, 297 ; m, PI. L, figs. 



810. 



Habitat. Jersey, Tide-marks, Westport Bay 



27. ISODICTYA SIMULANS (Johnston), n, 308 ; in, PI. LI, 

 figs. 5, 6. 



1861 Haliclona simulans, Bow. List Brit. Marine Invert. 



Fauna (Brit. Assoc.), p. 71. 

 1867 Adocia simulans, Gray. Proc. Zool. Soc., p. 522. 



Habitat. " Aberystwith, Mr. Bolton," purchased 

 by me from Mr. Ingall's collection ; Guernsey ; 

 Strangford Lough, 1869 ; Birterbuy Bay, Connemara, 



1875 



