1865.] DAWSON — COAL-FOEMATIOX. 97 



b. The Middle Coal- formation, or Coal-r)ieasures proper. — This 

 series includes the productive beds of coal, and is destitute of pro- 

 perly marine limestones. Beds tinged with peroxide of iron are less 

 common in this formation than in any of the others. Dark-coloured 

 shales and grey sandstones prevail, and there are no conglomerates. 

 Sigillarice and Stigmarice of many species are the most conspicuous 

 and abundant fossils, but Ferns, Cordaites, and Calamites are also 

 extremely abundant, and all the genera of Carboniferous plants are 

 represented. Many beds, especially those in the vicinity of layers of 

 coal, contain minute Entomostraca, shells of the genus Antliracomya 

 {Naiadites), Spirorlis carhonarius, and remains of ganoid and placoid 

 fishes. 



c. The "Millstone-grit^^ Formation. — This name, though not in 

 all cases Hthologically appropriate, has been borrowed from English 

 geology to designate the group of sandstones, shales, and conglome- 

 rates, destitute of coal, or nearly so, and with few fossil plants, which 

 underlies the Coal-measures. In its upper and middle part it in- 

 cludes thick beds of coarse grey sandstone holding prostrate trunks 

 of coniferous trees {Dadoxylon Acadianiim). In its lower part red 

 and comparatively soft beds prevail. 



d. The Lower Carboniferous Marine Formation. — The essential fea- 

 tures of this formation are thick beds of marine limestone, charac- 

 terized principally by numerous Brachiopods, especially Productus 

 Cora, P. semh^eticidatus, Atlujris suhtilita, and Terehratula suffiata*, 

 with other marine invertebrates. Associated with these limestones 

 are beds of gypsum, and they are enclosed in thick deposits of sand- 

 stone, clay, and marl, of prevailing red colours. 



e. The Lower Carboniferous Coal-measures, or Loiver Coal- 

 measures. — In some localities these resemble in mineral character 

 the true Coal-measures. In others they present a great thickness 

 of peculiar bituminous and calcareous shales. They usually contain 

 in their lower part thick beds of conglomerate, and coarse sandstone 

 which in some places prevail to the exclusion of the finer beds. 

 The characteristic plants of these beds are Lepidodendron corru- 

 gatum, and Cydopteris Acadica, with Dadoxylon antiquius, and 

 Alethopteris heterophyllaf. They also contain locally great quantities 

 of remains of fishes, and many Entomostracans, among which are 

 Leaia Leidyi and an Estheria, also Leperditia subrecta, Portlock, 

 Beyrichia coUicidus, Eichw., and a CythereX, probably new. 



The last two groups are equivalent to the " Sub -carboniferous " 

 of some American geologists; but independently of the objection to 

 the use of a term which would seem to imply a formation under, 

 and distinct from, the Carboniferous, and of undetermined age, I find 

 in Nova Scotia no reason, either palaeontological or stratigraphical, 

 for any greater distinction than that implied in the term Lower 



* See Davidson "On Lower Carboniferous Brachiopoda from Nova Scotia," 

 Quart. Journ. Geol. Soc. vol. xix. p. 158. 



t Dawson, " On the Lower Coal-measures," &c,, Quart. Journ. Geol. Soc. 

 vol. XV. p. 62. 



X Prof. Jones has kindly determined these species. 



