BRITISH SPONGIADiE. 45 



are found more deeply imbedded in the sponge ; they may, 

 therefore, be considered rather as subsidiary skeleton spicula 

 than defensive ones. The interstitial membranes are abun- 

 dantly present, they are thin and pellucid, and do not present 

 the slightest indications of tension spicula. 



Order II. SILICEA. 

 Genus. Geodia, Lamarck. 

 Geodia Zetlandica, Johnston. 



Axcyonium cydonil'm, Jameson. Wern. Mem., i, 563. 

 Cydonium Mulleei, Fleming. Brit. Animals, p. 516. 



Sponge. Massive, sessile ; surface even, strongly hirsute, 

 with large fusiformi-acerate and fusiformi-acuate spi- 

 cula projected at right angles to its plane. Dermal 

 membrane thin, translucent, spiculous, spicula atte- 

 nuato-stellate, abundant. Connecting spicula attenuato- 

 patento-ternate, stout ; and attenuato-recurvo-temate, 

 long, and slender, with rarely, slender porrecto-ternate 

 spicula. Oscula dispersed, or occasionally congregated. 

 Pores inconspicuous, minute, dispersed. Skeleton 

 spicula fusiformi-acerate, large. Spicula of the inter- 

 stitial membranes attenuato-stellate, variable in size ; 

 and also acerate, small, and slender. Gemmules 

 globose, slightly depressed. 



Habitat. Island of Fulah and Unst. Jameson. 



Cape of Good Hope ? Fleming. 

 Colour. Cream yellow. 

 Examined. In the dried state. 



The first record of this species is in Dr. Jameson's list of 

 Scottish vermes, ' Memoirs of the Wernerian Nat. Hist. 



