128 BRITISH SPONGIAD^. 



" In the dried state this sponge very closely resembles 

 some of the varieties of Ralichondria panicea in form, 

 in colour, in the shape of the spicula, and in the 

 possession of a reticulated dermal membrane, but the 

 examination of a thin slice of the sponge at right 

 angles to its surface immediately destroys the illusion ; 

 as the strongly produced scalariform structure of the 

 genus Isodictya in this species is totally unhke the skele- 

 ton structure of a specimen of Ralichondria panicea. 



" My friend the Rev. Mr. Norman states that this 

 species ' was found at Westport Bay under stones at 

 low-water spring tides August, 1875. This sponge is 

 very easily recognised when living. It is of a lemon- 

 yellow colour, and runs irregularly over the stones in 

 the form of large attached cloacal tubes, which here 

 and there expand into outspread patches of the 

 sponge from which arise several large upright cloacal 

 openings. The sponge is very soft to the touch, the 

 dermal membrane often much expanded with water, 

 having a remarkable membranous appearance to the 

 naked eye.' " 



31. IsODicTTA BowEEBANKi, Norman. 



ISODIOTYA SIMULO, BoW., II, 279; III, PI. XL VIII, 



figs. 11—13. 



Habitat. — Filling the interstices of Nullipora poly- 

 morpha, and sometimes growing long enough to com- 

 pletely cover the NuUipore ; dredged in Eoundstone 

 Bay, and under similar circumstances in Westport 

 Bay (N.). 



" Among the sponges I received from the Rev. A. 

 M. Norman, dredged on the western coast of Ireland, 



