BRITISH SPONGIAD^. 363 



with large and small bidentate equi-anchorate spicula, 

 irregularly dispersed. Skeleton. Spicula acuate, 

 stout, entirely, but incipiently spined. Internal de- 

 fensive spicula; sub-spinulate attenuato-acuate, en- 

 tirely, but incipiently spined. Interstitial membranes. 

 Tension spicula, acuate, slender, incipiently and en- 

 tirely spined ; and sub-mucronato-cylindrical, smooth 

 and slender. Retentive spicula ; large and small 

 bidentate equi-anchorate spicula. 



Colour. — In spirit, brownish red. 

 Locality.— Oban, Mr. Joshua Alder. 

 Examined. — From spirit. 



I am indebted for the only specimen of this species to 

 Mr. Joshua Alder, of Newcastle-on-Tyne, who obtained it 

 at Oban. It is nearly hemispherical in form, and is not 

 quite three quarters of an inch in diameter at its base. 

 In the wet state, the surface presents a granulated appear- 

 ance. The anchorate spicula on the inner surface of the 

 dermal membrane are attached at the middle of the outer 

 curve of the bow of the spiculum, so that both of the 

 fluked terminations are immersed in the surface of the 

 body of the sponge, and are equally well produced. The 

 small acuate spined and attenuated spicula closely resemble 

 those with which many species of fibrous sponges are armed, 

 and which are based in those species in the fibre, and pro- 

 ject at about right angles from it into the canals, and it is 

 probable they perform a similar defensive office in this 

 species ; but I could not find them in situ, although they 

 are tolerably abundant among the others when liberated 

 from the animal by boiling in nitric acid. I have, there- 

 fore, assigned them to the skeleton as defensive spicula by 

 analogy only. 



The sarcode is abundant and deeply coloured, and 

 abounds in granular molecules. 



