BRITISH SPONGTAD^. 251 



saburrata may be reckoned a mere variety of the species." 

 In tliis supposition I quite concur, and have therefore placed 

 it as a synonym of Hal. incrustans. 



Not having the advantages of a modern achromatic 

 microscope at the time he made his investigations, my 

 excellent friend Dr. Johnston was unable to detect the spi- 

 niferous character of the skeleton spicula, and the still more 

 minute bihamate and anchorate ones of the dermal 

 membrane. 



Among the British sponges with which I have been 

 favoured by the late Mrs. Griffith, there is a specimen of 

 H. incrustans, which was noted as having been "scarlet 

 but not foetid." In its dried state the colour was light- 

 yellow, the same as it usually is when in that condition. 

 Montague's description of this species under the designation 

 oi Sponffia fava, 'Wernerian Memoirs,' vol. ii, p. 115, is 

 exceedingly characteristic of its external appearances under 

 the circumstances described. 



15. Halichondria Candida, Bowerbank. 



Sponge. Massive, sessile, parasitical on small Fuci or 

 Zoophytes. Surface even sometimes tuberous, minutely 

 hispid. Oscula simple, dispersed, or slightly elevated. 

 Pores inconspicuous. Dermal membrane spiculous ; 

 spicula fusiform] -acuate, smooth, or rarely incipiently 

 spinous near the base, dispersed or diffusely fascicu- 

 lated, numerous ; retentive spicula contort bihamate, 

 small and slender, few in number. Skeleton. Strongly 

 compacted ; rete multispiculous, sides of the areas 

 rarely exceeding one spiculum in length j spicula 

 fusiformi-acuate, short and stout, entirely spined. In- 

 terstitial membranes pellucid, spiculous ; spicula same 

 as those of the dermal membrane, very few in number; 

 retentive spicula contort bihamate, small and slender, 

 few in number. 



Colour. — Alive, milk white. 



