1862.] JONES FOSSIL ESTHEKIJ2. 153 



Bed Sandstone of Cheshire, estimated by Mr. E. Hull at about 5350 

 feet. 



Isolated as these Lower Mesozoic shales of North America are, it is 

 difficult to co-ordinate them with the European scale of strata. They 

 are decidedly almost, if not quite, destitute of every trace of truly 

 marine agency, and must have been formed in long lagoons, or 

 brackish lakes, parallel with the Alleghany ridges (Rogers), under 

 somewhat similar condition to those which led to the formation of the 

 Lower Bunter of Alsace, the Lettenkohle of the Trias in Wiirtemberg, 

 &c, the lignitiferous and Estherian Upper Keuper of "Worcester- 

 shire and "Warwickshire, the Rhsetic Estherian shales of Gloucester- 

 shire and Morayshire, the coal-bearing beds of the Lower Lias of 

 the Banat, and the plant-beds and coal of the Lower Oolite of 

 Yorkshire and the Venetian Alps. The plant-beds with Estheria 

 in Bengal and Central India are similarly circumstanced. From the 

 time, then, of the Lower Trias to that of the Lower Oolite *, we see 

 that shallow lagoons, if not inland seas, of brackish water, largely pre- 

 vailed over some regions, and received the debris of a very similar flora ; 

 or we have before us the deposits of such waters, not truly contem- 

 poraneous, but presenting similar phenomena at different, but perhaps 

 not far distant, periods. To class all these as " Lower Mesozoic " will 

 be correct enough ; but it is hazardous to adjudicate definite geolo- 

 gical periods for all these several groups of strata. " Triassic " may 

 be the right term for the Indian and North American Estherian shales 

 and sandstones ; but the Rhaetic group may also claim them, as ex- 

 hibiting both Triassic and Jurassic belongings. Nor may we forget 

 that in all these instances we have to do with the freshwater fringes 

 or the lacustrine equivalents of the great marine formations ; which 

 latter alone, as Godwin- Austen has so cautiously insisted uponf, 

 should be strictly taken as the stratigraphical types, if, according to 

 the accepted rule, the geologic scale be based on the sea-conditions of 

 past periods. Thus the Old Red Sandstone and the Coal-measures 

 will take rank, as transitional and terrestrial formations, with the 

 Lettenkohle, the Jurassic and Cretaceous "Wealdens," and other 

 more or less freshwater deposits of marginal lagoons and deltas, or 

 of inland lakes, of the Primary, Secondary, and Tertiary periods, and 

 not stand as independent groups or systems. 



10. Estheria concentrica, Bean, sp., from the Plant-beds near Scar- 

 borough, is beautifully preserved in some instances, and at its first 

 discovery was recognized (by Mr. W. Bean, in 1836) as belonging to 



* Not that we are limited at this stage, except as regards the facies of the flora 

 referred to. Freshwater and estuary conditions, however prevalent in the Lower 

 Mesozoic period, were of equal importance in later Mesozoic times : not only in 

 the Middle Oolitic (Oxfordian),but in the Upper Oolitic and Cretaceous periode, 

 more or less known freshwater and terrestrial equivalents of the great marine 

 deposits spread far and wide in Europe and America (north and south) ; and in 

 the Tertiary formations, the freshwater and estuarine deposits have been fertile 

 sources of discussion with geologists and palaeontologists, who have often pre- 

 ferred a rich lake-deposit as a guide (however eccentric), in the puzzle-work of 

 correlation, to the more uniform sea-beds. 



t Quart. Journ. Geol. Soc. vol. xii. p. 54. 



