130 Canadian Record of Science. 



General form rounded, and probably when not changed by 

 pressure tumid. Anterior end broad and abruptly rounded ; 

 hinge line straight. Beaks raised and somewhat near the 

 front; lower and posterior margins broadly rounded, shell 

 thin, wrinkled when flattened, strongly marked with 

 growth-lines. 



This species resembles somewhat A. Adamsii var. expansa, 

 England. It is rare. Our only specimens are from McLel- 

 lan's Brook, Pictou, and Mabou, in Cape Breton, and are 

 mostly flattened, except some veiy young examples from 

 the latter place. 



In addition to fragments of plants and comminuted 

 debris of vegetable matter, the beds holding Naiadites, 

 contain a number of other animal remains, constituting a 

 peculiar fauna altogether different from that of the lower 

 carboniferous marine limestone, and also in many respects 

 distinct from that of the sandstones of the millstone grit 

 and upper coal formation. This fauna, though not that 

 which we would expect in fresh-water lakes or streams 

 under ordinary conditions, seems of such a nature as to be 

 appropriate to bodies of shallow, fresh or brackish water 

 loaded with vegetable matter, or to wide and sluggish 

 creeks traversing the great swamps of the period, and 

 occasionally widening into lagoons, receiving much fresh 

 water from the land, and having but little communication 

 with the open sea. The beds supposed to be thus deposited 

 are carbonaceous or bituminous shales and laminated, 

 impure limestones full of earthy matter, and blackened 

 with bituminous and carbonaceous debris. In addition to 

 the bivalve shells in question, they contain vast numbers 

 of minute bivalve crustaceans. (Bairdia and Carbonia) 1 

 Species of Eurypierus, Diplostylus and Anthropalaemon, 

 representing crustaceans of higher types. Great numbers 

 of the little Spirorbis carbonarius are also attached to many 

 of the plants and other fossils. Numerous scales and teeth 

 of ganoid fishes of the genera Palceonhcus, Bhizodus, &c, 



1 Rupert Jones, London Geological Magazine, August, 1894, p. 269, and June, 

 1889, p. 356. 



