PLATE LXXXIIT. 277 



defensive spicula ; those of M . fraudator being much 

 stouter, and their spination very much more strongly 

 produced, than in M. fictitia. 



The differences in the forms of the skeleton spicula are 

 sufficiently marked by those of M. fictitia being purely 

 acerate, long and slender, while those of M. fraudator 

 are stout and fusiformi-acerate ; the latter are not more 

 than half the length of the former. It is essentially 

 necessary in the discrimination of the two species that 

 these differential characters should be carefully noted, 

 as the general structure and the habits of the two are 

 so much alike ; and especially as the singular habit 

 described in the history of M. fictitia of the spreading 

 of the distal terminations of the skeleton columns on 

 the inner surface of the dermal membrane obtains in 

 both species. 



I have also received a specimen of this species from. 

 Mr. C. W. Peach, who found it in Fowey Harbour. 

 The sponge is not perfect. It is well represented by 

 the lower half of the figured specimen, but the diameter 

 is somewhat greater and there is a hole through it in a 

 longitudinal direction, indicating that, like the figured 

 specimen, it has grown surrounding the stem of a 

 fucus. 



CHALINA INORNATA, Bowerbank. 

 Plate LXXXIII. 



Sponge massive, sessile. Surface uneven. Oscula 

 and pores unknown. Dermal membrane sparingly 

 spiculous; spicula acuate, small and slender; rarely 

 the same form large and stout. Skeleton. Hete 

 rather coarse and open, irregular, abundantly spiculous, 

 spicula subfusiformi-acuate, very rarely acerate, small 

 and slender, numerous ; and the same form large and 

 long, few in number, near the circumference of the 

 fibre. Interstitial membranes sparingly spiculous ; 

 spicula same as those of the dermal membrane. 



Colour, ISTutbrown in the dried state. 



