The writer had the opportunity last summer, with Dr. B. J. Harrington as assistant, to re-examine the rock formations of Prince Edward Island, of which a notice was given in the second edition of his “Acadian Geology.” The report of our reconnaissance, which has been published by the local government, with a map, sections, and figures of fossils, may be referred to for details; but I propose in this paper to notice a few points of general scientific interest not dwelt on in the report.