(Plates XXII.—XXIV.) I. INTRODUCTION. In the summer of 1908 Mr. E. T. Paris and I spent some time visiting the principal sections of the Lower Oolites of Yorkshire with a view to seeing if it were possible to correlate these beds any more precisely than had already been done with those of the same series in the south-west of England. After my return, Mr. R. S. Herries very kindly lent me all the echinoids, brachiopods, and ammonites that he had collected from the Yorkshire Lower Oolites, and while Mr. Paris has named the echinoids, Mr. S. S. Buckman has identified the ammonites and has most kindly contributed two appendices to the present paper—the one descriptive of some ammonites from the Scarborough Limestone, the other comparing the uppermost Upper-Lias deposits in Yorkshire and the Cotteswolds. In Yorkshire the beds that intervene between the Cornbrash and the Upper Lias Clay are mainly sandstones and shales of estuarine origin, but with four marine bands, whose upper and lower limits are ofttimes none too well defined. They are :— [Cornbrash.] (1) The Scarborough Limestone. (2) The Millepore Limestone. (3) The Eller-Beck Bed, and (4) The Dogger. [The Blea-Wyke Beds.] In Table I. will be found detailed the principal sub-divisions that have been made of the Yorkshire Lower Oolites. Table I.—Sequence of the Lower Oolitic Rocks of the Yorkshire Coast. | (1) Shales, dark-coloured : a few foot thick at the Wyke, 6 to 8 feet thick in Newton Dale | | | || | (2) Limestone, dark | | |