322 A FHESH WATER SPONGE FROM SABLK ISLAND MACKAY. 



strands and their relationship to the other portions of the skele- 

 ton ; hut this crude provisional treatment of them suggested 

 that the filaments might be spongin fibres partly silicified, or 

 nascent siliceous spicules. 



The two classes of birotules arming the gemmule put the 

 sponge int'> Potts's genus Hete>-omeyenia. I therefore propose 

 the name Heteromeyenia macouni, in allusion to the distin- 

 guished naturalist who discovered it. It is possible that a com- 

 parison of the sponge with the two varieties referred to first 

 ab)ve as approximating to this species may reduce it to Hetero- 

 meyenia ryderi v. macouni ; but from the descriptions publish- 

 ed it appears to be specifically distinct. 



The sponge is especially interesting on account of its habitat 

 in the only fresh water pond of a sand island in the Atlantic 

 Ocean nearly 100 miles from the continent. The island is 

 about 20 miles long at present and about one mile broad. It 

 has been described as consisting of " two parallel ridges of loose 

 grey sand, in a bow or crescent shape, with the inner side to the 

 north. In the valley between these is a lake, now not more 

 than eight miles long, formerly nearly twice that length."* This 

 is the pond in which Heteromeyenia macouni has been growing 

 in abundance. 



* Sable Island : Its History and Phenomena, by Rev. George Patterson, D. D., in 

 Transactions of the Royal Society of Canada, Section II., 1894, (3). 



Date of Publication ; December 31st, 1900. 



