BRITISH SPONGIADJE. 319 



dispersed. Pores inconspicuous. Dermal membrane 

 aspiculous. Skeleton. Diffuse and irregular ; primary 

 lines loosely fasciculated, rarely more than trispicu- 

 lous, spicula acuate, long; secondary lines irregular, 

 sometimes more than unispiculous ; spicula acerate, 

 short. Interstitial membranes aspiculous. 



Colour. Alive, orange ; dried, nut-brown. 

 Locality. Off St. Martin's Point, Guernsey, Rev. A. 

 M. Norman ; Vazon Bay, Guernsey, Mr. Cooper. 

 Examined. In the dried state. 



The specimen is four and a half inches high, and six 

 inches in width ; the pedicel rather exceeds an inch in 

 height,, and is four lines in diameter, near the base ; the 

 branches are somewhat compressed, varying from four to 

 six lines in their greatest diameter, and they bifurcate at 

 short intervals in an irregular manner ; the whole of them 

 are nearly in the same plane, so that the form is rudely 

 fan-shaped, and where they meet near the middle of the 

 sponge they have anastomosed, forming a continuous surface 

 more than an inch in breadth and height. In the dried 

 state the surface is distinctly hispid, in consequence of the 

 prolongation of the primary lines of the skeleton, three or 

 four of the terminal spicula diverging at their distal termi- 

 nations at the surface of the sponge. The skeleton is very 

 irregular in its structure, especially in the deeply- seated 

 parts, which are open and cavernous to a considerable 

 extent, but near the external surface the structure is much 

 more regular. The acuate spicula of the primary lines are 

 about twice the length of the acerate ones of the secondary 

 lines ; and this difference in their form and size, combined 

 with the striking external characteristics of the sponge, 

 render the determination of the species comparatively easy 

 and certain. 



This species and I. infundihuliformis are the only two of 

 the genus with which I am acquainted in which the 

 primary lines of the spicula of the skeleton and those of 

 the secondary ones are of two distinctly different forms. 



