Deposits indicating the existence of the coal-flora and its associated freshwater fauna at the beginning of the Carboniferous period have been recognized in various parts both of the Old and New Worlds, and have modified the views entertained of the subdivisions of the Carboniferous system. In Nova Scotia and New Brunswick such deposits are developed with a clearness and fullness of detail capable of throwing much light on the dawn of the terrestrial conditions of the coal-period, and on the relations of these lower beds to the true coal-measures. I propose in the present paper to offer a contribution towards this end, by collecting in one view the information existing on these rocks in British America, with the addition of facts collected in the past summer, and the results of a comparison of the specimens in my collection with those of the upper portions of the coal-measures. I. Characters and extent of the Lower Carboniferous Rocks . The occurrence of beds containing coal-plants in connexion with the Lower Carboniferous marine deposits of Nova Scotia was observed by Sir W. E. Logan in 1841, though at that time the true place of the beds was not understood, owing to the belief that the limestones afterwards ascertained to be Lower Carboniferous were of Permian date. Sir C. Lyell examined these beds in 1842, as they occur at Horton Bluff; and the author subsequently more fully examined their relations to the marine limestones, and traced them in various parts of Nova Scotia, and at