ISODICTYA. 141 



the arrangement of the skeleton tissues much more 

 regular than in those of the type-specimen, while in 

 others the same confusion of the structures prevailed. 

 In all the anatomical characters these specimens were 

 in perfect accordance with those of the type-sponge, 

 excepting that there was a slight difference in the size 

 of the spicula. The spicula of the younger parts of 

 Mr, Norman's specimens were of the same size as 

 those of the type-specimen, but in the old and more 

 mature parts they were rather longer and stouter than 

 those of the type-sponge in the Liverpool Museum." 



55. ISODIOTYA IMITATA, Bow., Ill, 226, PL LXXVI, 



figs. 3—6. 



56. ISODIOTTA NODOSA, BoiD., n. Sp., IV, PI. XII, 



figs. 6—7. 



" Sponge massive, sessile, more or less nodose, para- 

 sitical. Surface minutely rugose. Oscula simple, 

 large, frequently terminating in nodous elevations. 

 Pores conspicuous, dispersed. Dermal membrane 

 pellucid, sparingly spiculous ; tension spicula sub-, 

 fusiformi-acuate, same as those of the skeleton. 

 Skeleton multispiculous, rather irregular, secondary 

 lines irregular, varying from unispiculous to bi- or tri- 

 spiculous ; spicula subfusiformi-acuate, minute, vari- 

 able in diameter. Interstitial membranes aspioulous. 



" Colour. — -In the dried state, light brown. 



"Habitat. — Birterbuy Bay, Ireland, Rev. A. M. 

 Norman. 



" Examined. — In the dried state. 



