144 BRITISH 



sible direction. The skeleton-rete is very regularly con- 

 structed, the primary lines consisting of from two or 

 three spicula in thickness to a greater number than can 

 be counted. The secondary lines rarely contain more 

 than two spicula at nearly equal distances, so that the 

 areas of the rete are nearly equal-sized oblongs. The 

 spicula are of a stout acuate form and are of nearly equal 

 size. The tension-spicula of the interstitial membranes 

 are like those of the dermis, and in some parts arc 

 rather numerously dispersed." 



58. ISODICTYA FERTENU1S, Bow., U. Sp., IV, PI. XIII, figS. 



14. 



" Sponge massive, sessile. Surface even, slightly 

 hirsute. Oscula simple, dispersed, few in number. 

 Pores inconspicuous. Dermal membrane spiculous ; 

 spicula dispersed, not very abundant, minutely acuate, 

 long and very slender. Skeleton-rete open and 

 very diffuse, rather irregular. Primary lines niulti- 

 spiculous ; secondary lines bi- or trispiculous ; spicula 

 minute, acuate, long and slender, very little larger 

 than that of the dermis. Interstitial membranes 

 sparingly spiculous ; spicula same as those of the 

 dermal membrane. 



" Colour. In the dried state, nut-brown. 



" Habitat. Tidemarks, Westport Bay, Co. Mayo, 

 1874; Rev. A. M. .Norman. 



" Examined. In the dried state. 



" There is nothing remarkable or especially charac- 

 teristic in the external appearance of this sponge, of 

 which there were three specimens. The largest example 



