37-i A MONOGRAPH OF THE 



Colour. Dried, dull green, yellow, or brown. 

 Habitat. Eastern and western coasts of England and 

 Scotland ; coasts of Ireland ; usually parasitical on Fuci. 

 Examined. In the dried state. 



This sponge is by no means a rare species. It is usually 

 parasitical on Fuci, and seldom exceeds a hazel-nut in size. 

 When small it has frequently but one osculum, but when 

 of larger size it has two or three, but rarely more. The 

 surface is hispid, by the projection of the distal terminations 

 of the primary lines of the skeleton. The dermal mem- 

 brane is smooth and pellucid, in some parts it appears to 

 be aspiculous, while in others the tension spicula are abun- 

 dant. The areas of the dermal reticulation are very much 

 larger than those of the skeleton structure. 



The skeleton fibres are cylindrical, and rather stout; they 

 are abundantly supplied with spicula, which are dispersed 

 excentrically, mostly in lines agreeing with the axis of the 

 fibre, but occasionally they cross each other at right angles 

 where a branch is given off. The primary lines of the 

 skeleton radiate from the base or centre of the sponge. 

 The secondary ones are at about right angles to the primary 

 ones, but they are frequently very irregular. The dis- 

 position of the spicula in the fibre is very remarkable in 

 this sponge ; there is no approach to the axial arrangement 

 so distinctly exhibited in the fibres of other species of this 

 genus, but they appear to be disposed in all parts of the 

 fibre, so as to simulate the structure of a Desmacidon, but 

 with this distinction, that whether few or many they are 

 always the subordinate material in the construction of the 

 fibre, and never appear to influence its form and propor- 

 tions as in a Desmacidon, and in the young and slender, 

 but perfectly formed fibres there are frequently no spicula 

 present. 



A small encrusting specimen of this sponge was sent me 

 by Mr. Alder, who found it at Cullercoats. It had the 

 dermal and other membranes in good condition ; immersed 

 in water, a small portion exhibited an appearance of spicula 

 imbedded in the sarcode with which the membranes were 



