392 <A FRESH WATER SPONGE FROM SABLE ISLAND —MACKAY. 
strands and their relationship to the other portions of the skele- 
ion; but 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 into Potts’s genus Heteromeyenia. I therefore propose 
the name Heteromeyeniu macourn?, 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 
above as approximating to this species may reduce it to Hetero- 
meyenia ryderi v. MucoUnt ; 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 macount has been growing 
in abundance. 
ne 
* Sable Island: Its History and Phenomena, by Rey, George Patterson, Diu 
Transactions of the Royal Society of Canada, Section II., 1894, (3). 
