The Inferior Oolite of the Cotteswold Hills, with special Reference to its Microscopical Structure

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Abstract
P art I.—T he G eneral S tructure . (a) Introduction T he main divisions of the Inferior Oolite in the Cotteswold Hills are known to geologists who have made a study of Jurassic rocks, but to those who have not done so and to foreigners they may be less familiar. In order, therefore, that my remarks may be the more easily understood, I indicate the following main divisions which I propose to adopt, deferring my explanations of them till later on. They are given in descending order :— Ragstones. Upper Freestones. Ragstones Oolite Marl. Lower Freestones. Pea Grit. Transition Beds, resting on the Upper Lias. (b) The Transition Beds . Position and General Structure .—There has been considerable discussion among geologists as to where the line is to be drawn between the Inferior Oolite and the Upper Lias. To give even a summary of the controversy would take up considerable space and tend to divert the reader's attention from the primary object of this paper. I will, therefore, only mention the views of two geologists who may be said to represent the respective contentions. The late Dr. Wright, F.R.S., referring to the zone of Harpoceras opalinum , said : “This zone was formerly grouped with the Cephalopods-bed of Frocester ; but, as it contains some species which are limited to this horizon and are associates of H. opalinum , it is best to

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