242 Organic Siliceous Remains. 



This induction is as yet based on too few a number of observ- 

 ations to be of any scientific value. But such instances as the 

 following have been observed : Melosira arenaria (Moor) is 

 abundant in the Earltown Lakes near the summit of the Cobequid 

 range of mountains ; while Gulley Lake, a few miles on the other 

 side of the watershed, is distinguished by the presence of Stenop- 

 terobia anceps (Lewis) Breb. ; and Mackintosh Lake, separated 

 only by a few miles of mountain ridge and forest from both, con- 

 tains, apparently neither this species of Melosira nor Stenopterobia ; 

 and the deposits of Lochaber lake are characterized by the rela- 

 tive abundance of Cydotella. Of course these lake deposits con- 

 tain, not only the organisms which live in their own waters, but 

 those which are swept a into them by their tributary streams. 



In addition to the remains of the diatomaceae, the siliceous 

 spicules of sponges abound in all these deposits, especially the long 

 skeletal spicules. In some few places, the silica from this source 

 is in excess of that from the diatomacese. A search for the origin 

 of these having been made last summer no less than nine species 

 in four genera have been found, and two of these are con- 

 sidered as new*to science. These fresh-water sponges grow on 

 submerged wood, plants, stones and even on sand. They are all of 

 some hue of green when living and exposed to the influence of 

 light. They vary in size from very small up to a specimen of 

 Meyenia fluviatilis, growing in Grarden-of-Eden Lake, which mea- 

 sured twenty-seven inches in length by four inches in diameter, 

 surrounding a small branch as a core. In the winter season the 

 flesh of these generally decays, and most of the skeletal 

 spicules scatter and accumulate in the adjacent deposits. The 

 reproductive gemmules with their characteristic spicules, also, in 

 the course of time float away, or germinate next spring on the 

 original site. The following are the species of siliceous sponges 

 which have been identified as living in the lakes at present, and 

 whose spicules abound in the deposits under consideration. These 

 sponges, like the diatoms, have certain species characteristic of 

 certain waters, while others are more generally distributed. 



1. Spongilla fragilis, Leidy. 



2. S. lacustris var. dawsoni, Bk. 



3. S. mackayi, Carter. 



4. Meyenia fluviatilis, Carter. 



