T he boring of the Subwealden Exploration has brought into prominence the antiquity of our information concerning the Kimmeridge Clay of England, both as to its subdivisions and as to its thickness. The only recent work done upon it is that of a foreigner, Dr. Waagen, who, studying it on the southern coast at Ringstead Bay and at Weymouth, proposed a new classification, which has been followed by Mr. Judd in his valuable paper on the Speeton clay. With this exception we have to go back to the days of Conybeare and Buckland for information on the subject; and it has been impossible for foreign authors to correlate satisfactorily their Kimmeridgian beds with ours. Dr. Waagen’s paper is brief and incomplete; and there thus seemed room for useful observation on this subject. Both the above-named authors, as well as Professor Phillips and Mr. Damon, have made additions to our list of fossils; but the two latter have only indicated local subdivisions in the beds. On the Continent, though much diversity exists in the arrangement of these beds (each separate locality having palæontological features which, to a certain extent, render unavailable the classification founded on others), the general result is their separation into three zones—the lowest that of Astarte supracorallina , or theAstartian, and the middle that of Pterocera Oceani , or the Pterocerian. On these two there is considerable uniformity of opinion; while the upper, more or less developed in various localities, is either included in the zone of Trigonia gibbosa , or the