122 A MONOGRAPH OF THE 



every imaginable angle, thus forming an irregular but 

 strong connecting network of spicula between the neigh- 

 bouring secondary ramuli. 



2. Phakellia ventilabrum, Bowerbank. 



Halichondkia ventilabrum, Johnston. 



Sponge. Cyathiform or ventilabriform, elevated on a short 

 pedicle ; distal margin attenuated to a sharp edge. Sur- 

 faces smooth or somewhat rugose and excavated, 

 minutely hispid. Oscula simple, dispersed, numerous 

 and minute. Pores inconspicuous. Dermal mem- 

 brane aspiculous. Skeleton : spicula of the axes 

 cylindrical, long, slender, and very flexuous ; of the 

 ramuli acuate, slender, rather long, and frequently 

 slightly flexuous. External defensive spicula same as 

 those of the ramuli. 



Colour. Pale yellow, with a tint of green, preserved in 

 strong salt and water while alive. 



Habitat. Haaf Banks, Shetland, Mr. Barlee and Mr. 

 Humphreys ; Loch Pine, Rev. A. M. Norman. 



Examined. Presh and undried, as from the sea. 



The description of the external characters of this sponge 

 given by Dr. Fleming is very correct applied to dried 

 specimens only, but it may be as well to remark that the 

 difference between the fresh and the dried specimens is so 

 great as to quite alter the specific characters derived from 

 these sources. Thus, specimens which in the former con- 

 dition have the surfaces smooth and imperforate, when 

 dried become highly villous and present quite a reticulated 

 and perforated appearance, in consequence of the contrac- 

 tion of the interstitial tissues, and the real oscula are undis- 

 tinguishable amidst the numerous fractures arising from 

 this cause. In young and well-preserved specimens, which 

 have not been dried, the surface is usually smooth and even, 



