88 A MONOGRAPH OF THE 



Connecting spicula attenuato-recurvo-patento-ternate ; 

 radii short, stout, and abruptly recurved near their 

 apices. Skeleton. Spicula fusiformi-acerate, stout. 

 External defensive spicula fusiformi-acerate, short, and 

 slender. Interstitial membranes. Tension spicula, 

 acerate, slender ; retentive spicula, same as those of 

 the dermal membrane, very abundant. 



Colour. Alive. External, somewhat green ; internally, 

 light gray. 



Habitat. Guliot Caves, Sark, J. S. Bowerbank ; Round- 

 stone Head, near Paignton, Torbay, Mr. Gosse ; Tremain 

 Bay, Guernsey, fifteen fathoms, Rev. A. M. Norman. 



Examined. In the living state. 



I received a portion of this sponge from the late Mrs. 

 Buckland, who, I believe, obtained it from Mrs. Collings, 

 the lady of the Seigneur of Sark ; and in 1860, I found 

 the specimens I have described in the second of the Guliot 

 Caves at Sark. I believe it to be of rare occurrence, and 

 it was very difficult to distinguish it from the well covered 

 surface of the rock to which it was strongly and broadly 

 attached. The specimen I have is not above half its own 

 diameter in height. It has a broad, flat, uneven surface, 

 nearly two inches in diameter, with a deep cavity near its 

 centre, and has much more of the aspect of a coating 

 species of Geodia or Pachymatisma than that of the normal 

 bulbous form of a Tethea. 



The dermal coat is very dense, and in some parts it 

 rather exceeded two lines in thickness. The connecting 

 spicula are fasciculated, their bases converging to and 

 uniting with the radial fasciculi of the skeleton where their 

 distal terminations are radiated in all directions until they 

 reach nearly the inner surface of the dermal membrane 

 through which they rarely pass. A second and a more irre- 

 gular series of ternate spicula exist immediately beneath 

 the inner surface, and their recurved radii are frequently 

 projected into the intermarginal cavities of the sponge, 

 apparently effecting the office of defensive spicula in those 



