Bivalve Shells of Nova Scotia. 131 



also occur, and teeth of dipnoid fishes (^tenodus), also various 

 species of sharks (Ctenoptychius, Psammodus, Diplodus, &c). 

 Some of these sharks must have attained to a considerable 

 size, and they no doubt found access to the inland waters 

 by the outlets communicating with the sea, and were 

 attracted to visit these comparatively impure lagoons by 

 the abundance of food which they afforded. l Very rarely 

 there have been found in these beds bones of amphibians 

 and shells of pulmonate snails, (Pupa vttusla, &c). Animals 

 of these kinds no doubt haunted the margins of the lagoons 

 or creeks; but only occasionally left their remains in 

 deposits accumulating in these places. 



We perhaps obtain a glimpse of purer inland waters, 

 similar to those of modern Canadian lakes, by means of a 

 remarkable shell, discovered by Mr. Weston, of the Geo- 

 logical Survey, at the South Joggins in 1893, and which 

 has been described by Mr. Whiteaves, F.G.S., under the 

 name Asthenodcnta Westoni. " It resembles in general form 

 the large pearl-mussel of our modern lakes. (Margaritana 

 margaritifera L.) and some specimens are no less than nine 

 inches in length, and of somewhat massive thickness 

 anteriorly. It was found in a sandstone with drift trunks 

 of trees, and may have come from some distance inland. 

 Such a shell could scarcely have been a companion of our 

 little Naiadites or Anthrocomyse, and points to more favor- 

 able conditions for fresh-water molluscan life in lakes or 

 large streams in the interior of the continent. 



Conditions favourable to such mollusks were probably, as 

 I have elsewhere suggested, more prevalent in the later 

 Erian or Devonian than in the Carboniferous. Hence the 

 occurrence of such large Anodon-like shells as Amnigenia 

 Cattskillensis, Hall in New York, and Anodon Jukesii in the 

 Kiltorcan beds in Ireland. The above discovery however now 

 gives reason to believe in similar conditions as existing in 

 higher grounds contemporaneously with the great coal 

 swamps of the low plains of the carboniferous period. 



1 Notices of this fauna will be found in Acadian geology, pp. 202 et seq., 

 and supplements. 



'-' Trans- Royal Society of Canada, Section iv, 1892 



