PLATE XCI. 83o 



acuatc, basally spinous, or sparingly entirely spinous. 

 Interstitial luembranes. Tension spicula same as 

 tliose of dermal membrane, few in number, dis- 

 persed ; retentive spicula, same as tliose of dermal 

 membrane. 



Colour. — In tlie dried state, dull oclireous yellow. 



Habited. — Diamond ground off Hastings ; J. S. Bower- 

 bank. 



Examined. — In tlie dried state. 



I received two small specimens of this sponge 

 parasitical on tbe same slender stems of a fucus ; the 

 specimens are separated from each other by about half 

 an inch. In every resiject they very closely resemble 

 each other, the surfaces of both being remarkably 

 rugged and uneven. The oscula are mostly situated 

 in the deepest portions of the rugged surface; they are 

 not readily to be detected without close observation, or 

 by the aid of a lens. The distribution of the tension 

 spicula on the dermal membrane is very irregular. On 

 the sides of some of the deep depressions of the surface 

 they are very regularly disposed in parallel flat bundles, 

 while on other parts their disposition is quite irregular, 

 but in all their conditions they are very characteristic. 

 They are equal in length, but much more slender than 

 the skeleton spicula, and they are perfectly free of 

 spines. 



There is a great disparity in the sizes of both the 

 bidentate equi-anchorate and the bihamate retentive 

 spicula. Some of the anchorate spicula are remark- 

 ably large and strong in their proportions ; one of the 

 largest measured g-^y- inch, in length and the diameter 

 of the shaft was sifoiJ inch, while one of the smallest of 

 the same form was but 2-^00" i^^h in length ; the 

 smaller forms are very much more numerous than 

 the large ones. These spicula are very puzzling 

 objects, even beneath a power of five or six hundred 

 linear. 



It is very rarely that both of the teeth at each termi- 

 nation of the spiculum can be distinctly defined. 



