238 PLATE LXSVII. 



peated observations have led to the conclusion that 

 under favorable circumstances the congregated groups 

 are found to be anything rather than at distant intervals. 

 In one specimen of a portion of dermal membrane 

 from the specimen figured, in a field, with a linear 

 power of 80, ^3 i^^cli in diameter, I counted as many as 

 forty of these beautiful groups. They were rather 

 evenly dispersed, and the intervals were crowded with 

 innumerable smaller forms of the same description of 

 spicula irregularly dispersed, mixed with equally nu- 

 merous bihamate spicula. In some parts of the same 

 piece of dermal membrane the rosette groups were 

 clustered together so thickly as to form quite an irre- 

 gular mass of intermixed spicula. 



The structures of the dermis of this sponge are 

 strikingly characteristic. The rete is coarse and very 

 strongly produced ; it is formed of large and long- 

 fasciculi, each containing numerous closely packed sub- 

 fusiformi-acuate spicula, so as neai'ly to resemble the 

 fibre of a Desmacidon at the middle, but none of these 

 bundles are continuous ; they form the reticulation by 

 crossing each other, usually in a diagonal direction, 

 producing elongate ai-eas like those of a net extended 

 in one direction only ; the spicula are the same size as 

 those of the skeleton. 



The dermal membrane is literally crowded with 

 bihamate sjjicula, which completely conceal the nu- 

 merous slender tension spicula intermixed with them ; 

 and occasionally, but rather rarely, a solitary inequi- 

 anchorate spiculum may be seen among them, or two 

 or three together, forming an immature radial group. 

 The curve of the bihamate spicula is nearly semi- 

 circular, and the shaft equable and very slender. The 

 dentato-palmate inequi-anchorate spicula of the radial 

 groups are large and well produced ; they very closely 

 resemble fig. 147, Plate VI, vol. i, ' Mou. Brit. 

 Spongiada3.' The dispersed spicula of the same form are 

 not so Avcll developed, and are very much less in size. 



The general character of the reticulations of the 



