The oilfields of Burma lie almost entirely within the elongated Tertiary basin which runs approximately north-south and is bordered on the west by the Arakan Yoma and on the east by the ancient plateau of the Shan Hills. Most of the oil has been obtained from fields lying on a single line of folding and in a belt only 50 miles long between latitudes 20° 20′ and 21° 10′, the remainder being found in small fields situated at various places between latitudes 19° 25′ and 23° 45′.

The outcrop of Dogger described in this paper covers an area 12 miles in length, stretching S.S.W. from Whitby up the lower course of the River Esk and its tributary valleys of Iburndale, the Murk Esk Valley, Egton Grange, and Glaisdale. Unlike the coast natural exposures are few and unsatisfactory and in Lower Eskdale in particular are only encountered where becks from the surrounding moors cut through the massive boulder clay plug which partly fills the main valley. Other exposures occur in abandoned alum works, disused ironstone adits and small quarries. The outcrops cross diametrically a part of the Whitby Basin, the Eskdale Dome, the Goathland Syncline, notch the main Cleveland Dome (Lees and Cox, 1937),1 and range in height from 35 to 500 feet O.D..

Biconvex to plano-convex usually partly costate Protremata, without pseudodeltidiuin or chilidium so far as known. Of the two valves the dorsal is considerably the larger and more convex. The delthyrium is closed by the incurved dorsal umbo. Dentition simple; strong teeth developed on dental-plates fit into sockets between the brachial-processes and the valve margin. The dental-plates unite to form a duplex spondylium. In the dorsal valve the alate cardinalia consist of short brachial-processes supported on outer-plates, which may remain parallel or converge to form a sessile cruralium or cruralium duplex. The muscles are attached within the spondylium in the ventral valve, while dorsally there is a central grouping of the adductor muscles on the inner surface of the valve below the cruralium.