Vol. 50.] NAIADITES FROM NOVA SCOTIA. 435 



27. Note on the Genus Naiadites, as occurring in the Coal Forma- 

 tion of Nova Scotia. By Sir J. William Dawson, C.M.G., 

 LL.D., F.R.S., F.G.S. With an Appendix by Wheelton 

 Hind, M.D., B.S., F.B.C.S., F.G.S. (Read February 21st, 

 1891.) 



[Plate XX.] 



In the autumn of 1892 Dr. Wheelton Hind was so kind as to invite 

 me to place in his hands, for study and comparison, specimens of the 

 bivalve shells from the Coal Formation of Nova Scotia, which I had 

 described under the above generic name, 1 and some of which were 

 described by the late Mr. Salter in the Quarterly Journal of this 

 Society, vol. xix. (1863), under his new generic names Anthracoptera 

 and Anthracomya. Owing to illness I was unable, at the time, to 

 comply with Dr. Hind's request, and thus the Nova Scotian species 

 lost the benefit of a detailed comparison with the British forms in 

 Dr. Hind's excellent paper of May 1893." I have now sent a col- 

 lection of specimens to him, and beg to make the following remarks 

 thereon. 



These shells occur plentifully in some of the argillaceous shales 

 of the Coal Formation, and occasionally on the surfaces of flaggy 

 sandstones, but the most abundant repositories are the beds which 

 I have named ' calcareo-bituminous shales' and 'bituminous lime- 

 stones,' beds which, on account of their superior toughness and 

 black colour, often stand out prominently in the coast-sections, and 

 are sometimes almost entirely composed of these shells. a As none 

 of the properly marine species of the Carboniferous Limestone ever 

 occur in these beds, and as they are closely associated with the coal- 

 seams, I have always been greatly interested in them — in connexion 

 with the various theories of the deposition of coal. I referred to 

 them in this relation in ' Acadian Geology,' 2nd ed. 1868, 4 in the 

 following terms : — 



" All the lamellibranchiate shells, which are so numerous in some 

 of the shales and bituminous limestones of the Joggins that some 

 of the beds may be regarded as composed of them, belong to one 

 generic or family group. They are the so-called Modiolas, Unios, 

 or Anodons of authors. I proposed for them, some years ago, 

 the generic name of Naiadites,* and described six species from 

 the Coal Measures of Nova Scotia, stating my belief that they are 

 allied to Unionidae, and that their nearest analogue may be the 

 genus Bysso-anodonta of D'Orbigny, found in the river Parana. 



J ' Acadian Geology,' Suppl. 1st ed., I860. 



2 Quart. Journ. Geol. Soc. vol. xlix. p. 249. 



3 See section of the South Joggins, in ' Acadian Geology,' 2nd and later 

 editions. 



4 Pp. 202, 203. 



5 'Acadian Geology,' Suppl. 1st ed. 



