Vol. 50.] THE COAL-FORMATION OP NOVA SCOTIA. 437 



to depend upon. The species seem also to have been very variable, 

 and they present very different appearances in different states of 

 compression. 



I may also mention that Dr. Wheelton Hind has been led into 

 an error in supposing that Estheria Dawsoni, described by Prof. T. 

 Rupert Jones, F.R.S., in the Geol. Mag. for 1870, may be the same 

 with my Naiadites Icevis. These shells are quite distinct in forms, 

 markings, and structure, and occur at very different positions in the 

 Carboniferous. N Icevis has been found only in a flattened state : 

 its epidermis is strong and wrinkled, and the shell shows traces 

 of prismatic structure. 



The associates of Naiadites in the admirably exposed sections of 

 the Nova Scotian coal-field, at the South Joggins and Sydney, Cape 

 Breton, are various species of minute bivalve crustaceans, Eury- 

 pterids, Antlirapalcemon? scales and teeth of ganoid fishes, and 

 Spirorbis. The beds also hold much carbonaceous matter and 

 fragments of fossil plants, often with Spirorbis attached. In some 

 cases the beds of Naiadites-shale form the roofs of small coal-seams. 

 In a few they have been elevated into soils and have been pervaded 

 with Stigmaria-roots, thus resembling underclays. Their whole 

 conditions point to land-locked ponds or lagoons, or to sluggish creeks. 

 From the continuity of the beds these would appear sometimes to 

 have been extensive, and, in addition to the animals already referred 

 to, they were visited by ganoid fishes of large size, of the genus 

 Rhizodus, and by small sharks of the genus Diplodus (Or acanthus). 

 They were also tenanted by the aquatic batrachians of the period. 



As the supposition that the shells of Naiadites were marine 

 has placed them out of relation with their associates in the Coal 

 Formation of Nova Scotia, it is a source of gratification to me, and 

 an important contribution to the theory of coal, that their true 

 affinities have now been so ably illustrated by Dr. Wheelton Hind. 



Appendix. 



Through the courtesy and kindness of Sir J. William Dawson I have 

 been favoured with a perusal of his ' Note on the Genus Naiadites' 

 and have carefully examined at his request a series of shells from the 

 South Joggins, as well as a series from the collection of the Geological 

 Survey of Canada, forwarded to me for that purpose. 



From an examination of these specimens it is easy to understand 

 Sir William's attitude in considering it impossible to discriminate 

 with any certainty between the different genera of shells in the 

 South Joggins coal-field. They were all more or less crushed in the 

 shale, and therefore showed no interiors, and often the proper 

 external characters were masked. I am quite of the opinion now, 

 from the knowledge I have obtained by a long familiarity with 

 nearly perfect forms, that the genus Naiadites contains three distinct 

 genera, for one of which the name must be retained. These three 

 genera are the same as those which generally occur in our Coal 



1 A. miliaria, Geol. Mag. 1877, p. 56. 



