120 A MONOGRAPH OF THE 



increase considerably in number as they progress towards 

 the surface, where a few of the terminal ones passing for a 

 short distance through the dermal membrane act as external 

 defensive spicula, rendering the surface, in the fresh state, 

 very slightly hispid, but in the dried condition this character 

 becomes, by contraction, exceedingly prominent. 



Mr. Barlee dredged this species in sixty to seventy 

 fathoms, about twenty-five miles off Lerwick, near the outer 

 skerries ; and I obtained about sixty or seventy specimens, 

 preserved in salt and water, from the Shetland fishermen, 

 who brought them up with hooks and lines while fishing in 

 sixty or seventy fathoms at the Haaf Banks. In drying, 

 this sponge assumes a deeper yellow colour than it has in 

 the wet state. 



Genus — Phakellia, Bowerbank. 



1. Phakellia robmta, Bowerbank. 



2. — ventilabrum, Bowerbank. 



1 . Phakellia robusta, Bowerbank. 



Sponge. Fan-shaped, elevated on a short pedicle ; distal 

 margin attenuated to a sharp edge, surface smooth 

 or very slightly hispid. Oscula simple, dispersed, 

 numerous, and small. Pores inconspicuous. Dermal 

 membrane aspiculous. Skeleton : axial column very 

 slender; spicula acuate or acerate, large and long, 

 flexuous ; ramuli diffuse ; spicula stout, rather short, 

 acuate, occasionally acerate. Interstitial tension 

 spicula very large and strong, rather numerous, 

 mostly acerate, occasionally acuate, very flexuous, 

 passing at various angles from one radial fasciculus to 

 another. 



