BRITISH SPONGIADiE. 71 



7. Polymastia mammili.aris, Bowerbank. 



Spongia pbnicillus, Montagu. 



HaLICHONSBIA MAMMILIiABIS, Johltston. 



Sponge. Massive, sessile. Surface even, hispid. Oscula 

 terminal, congregated on slender mammaeform cloacal 

 fistulse ; rarely simple. Pores inconspicuous. Dermis 

 of the basal mass sub-crustular. Dermal membrane 

 pellucid, aspiculous. Dermis of the cloacal fistulse 

 furnished abundantly with radiating fasciculi of 

 secondary external defensive spicula ; spicula based on 

 the external surface. Skeleton. Pistulse numerous, 

 strap-shaped, frequently truncated, or somewhat ex- 

 panded at their distal terminations. Spicula of the 

 primary fasciculi fusiformi-enormi-spinulate, rarely 

 fusiformi-acuate, long and stout. External defensive 

 spicula of basal mass, same as those of the skeleton. 

 External defensive spicula of fistulse fusiformi-spinu- 

 late, short and small, very numerous ; congregated in 

 radiating fasciculi, and based on the dermal mem- 

 brane. Tension spicula fusiformi-spinulate, variable 

 in size. 



Colour. — Light ochreous yellow, 



Habitat. — Lame Lough, Mr. Hyndman; Guernsey, 

 Rev. A. M. Norman; Shetland, Mr. Barlee; Orkney 

 Islands, Capt. F. W. L. Thomas, R.N. 



Examined. — In the fresh and dried states. 



I am indebted to my friend, Mr. George Hyndman, of 

 Belfast, for two fine specimens of this species, each about 

 two and a half inches in diameter, and about half an inch 

 in thickness. Both have the appearance of having coated 

 water-worn stones. The cloacal fistulse are very abundant 

 on both specimens ; their average length is about six or 

 seven lines, and their width a line and a half; they" are 

 compressed for the whole of their length, and the distal 



