BRITISH SPONGIADjE. 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, 



AiiCTONiuM cydonium, JatMson. Wern. Mem., i, 563. 

 Ctdonium 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-ternate, 

 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 ? Plemiag. 

 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. 



