BRITISH SPONGIAD^. 293 



latter, although of the same length as those of /. densa, are 

 considerably less in their diameter, and in /. densa we do 

 not observe the large irregularly shaped porous areas in the 

 dermal membrane, which are so characteristic in /. indis- 

 tincta. 



The skeleton spicula of /. simulo are also of about the 

 same length as those of J. densa, but they are still more 

 slender than those of /. indistincta. 



The sarcode has been very abundant, and in its present 

 condition is of a dark amber colour. 



13. IsoDlCTYA ANOMALA, Bowerbank. 



Sponge. Massive, sessile ; surface even. Oscula few, 

 large, simple. Pores unknown. Dermal membrane, 

 unknown. Skeleton. Primary lines multispiculous, 

 very large and compact ; secondary lines, usually a 

 single spiculum ; spicula inflato-fusiformi-acerate, short 

 and stout. Interstitial membranes. Tension spicula, 

 acerate, slender. 



Colour. — 'Dried, yellowish- gray. 

 Habitat-^Toxhaj, Mrs. Griffiths. 

 Uxamined.-^ln the dried state. 



The sponge which is the type of the above species is in 

 truth but a fragment, apparently about the eighth part of 

 a mass, having been about the size and form of a large 

 walnut ; or it may have received its curved and somewhat 

 concave form by having partially surrounded the stem of a 

 large Pucus ; it is eight lines in diameter, and does not 

 exceed three in thickness. Por the depth of a line and a 

 half from the surface the skeleton is composed of a series 

 qf stout parallel primary fasciculi of spicula, connected by 

 secondary fasciculi, usually of single spicula, and poly* 

 spiculous, and the spicula composing them are remarkably 

 stout in proportion to their length, and very variable in 

 their fusiform structure: the amount of central inflation 



