. The Quarterly journal of the Geological Society of London . ngabout the lowest seen. The beds exposed in the railway-section nearTefFont include the base of the Wealden, all the Middle Purbecks ofthe Yale of Wardour, and the top of the Lower Purbecks. The middlegroup here is about the same thickness as the beds in the Isle ofPurbeck ; those at Eidgway Hill and Mewps Bay are about 50 ft.;and at Worborrow Bay the middle series measures 90 ft., and atDurlston Bay 150 ft. There is no Upper Purbeck in the areaunder observation ; the hard marl with eroded surface is the highestmember of the Middle
. The Quarterly journal of the Geological Society of London . ngabout the lowest seen. The beds exposed in the railway-section nearTefFont include the base of the Wealden, all the Middle Purbecks ofthe Yale of Wardour, and the top of the Lower Purbecks. The middlegroup here is about the same thickness as the beds in the Isle ofPurbeck ; those at Eidgway Hill and Mewps Bay are about 50 ft.;and at Worborrow Bay the middle series measures 90 ft., and atDurlston Bay 150 ft. There is no Upper Purbeck in the areaunder observation ; the hard marl with eroded surface is the highestmember of the Middle Purbeck, the succeeding 17 ft. being probablyHastings Sand at the base of the Wealden. densinoda, Ether. (Eig. 1.) Shell greatly elongated or lengthened posteally, the anteal or PTTEBECK BEDS OF THE VALE OE WARD OUR. 247 anterior side rounded and somewhat steep; the base (inferior orventral border) flattened; the postero-dorsal (nmbonal or superior)border concave and much elongated. Tig. 1.—Tritjonia densinoda, Umhones pointed, small, but prominent or elevated and slightlyrecurved, antero-mesial, or placed within the anterior third of thevalves. Area moderately wide, flattened and filled with reticulated costellae,which are minutely and delicately nodulated or tuberculated; it isbounded by two carinae, the outer densely or closely nodulated, in-creasing in width from the umbo to near the extremity of the pos-teal side, then merging into the system of tuberculated transversecostse; or the extreme posteal border possesses many irregular linesof growth due to the elongation of the tubercles. The innercarina, or that bordering the escutcheon, consists of a series of minutetubercles which are immediately surmounted by the tranverse wavyridges of the escutcheon. The median sulcus, or mesial furrow,is well defined. The escutcheon is remarkably large, having trans-verse wavy rugse resembling those occurring in the INeocomian Qua-dratse. T
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Keywords: ., bookcentury1800, bookdecade1840, bookidquarte, booksubjectgeology
