

THE JURASSIC SYSTKM 429 



( '</</, and Viviparus. The thickness of the vvliole group is 200 



B. Grey and white .sandstones, sometimes passing into calcareous 

 k r rits, with large concretionary siliceous nmsses ; current-bedding 

 and ripple - marked surfaces are frequent, but excepting plant 

 ivmains fossils are rare. Thickness probably more than 500 feet. 



C. The highest beds are black shales with thin bands of 

 argillaceous limestone and bands of fibrous carbonate of lime ; they 

 are sometimes crowded with Cyrena and Cyclas, and in other places 

 with Viviparus, Melania, and other Gastropoda. Beds entirely 

 composed of oysters (0. hebridica) also occur, resembling those in 

 the Purbeck Series (see posted). Thickness 150 feet 



2. East Coast 



Beds of Middle Jurassic age occupy a small space on the coast 

 of Sutherland south of Brora, and form two small patches at Burgh 

 Head and Stotfield, on the coast of Elgin. They consist entirely 

 of estuarine strata, which are lithologically comparable to those of 

 the Great Oolite Group on the western coast. The descending 

 succession near Brora is as follows : 



Feet. 



" Roof bed," calcareous sandstone (Kellaway) . . . . ~\ , 



Coal composed of crushed Equisetites . . . . . / 

 Black shales with thin coal-seams in the upper part, plants, 

 and crushed shells of Unio, Ostrea, Cyrena, etc., abound; 

 also teeth and scales of fish, Lepidotus, Pholidophorus, and 



Hybodus 26 



Black, brown, and grey clays with layers of argillaceous lime- 

 stone, Cyrena and Ostrea ....... 96 



White sandstones with some beds of clay ; in this a few 



obscure marine shells occur . . . . . .110 



The base is not seen, and whether any beds comparable to the 

 Inferior Oolite of the west coast exist below is, therefore, unknown. 

 At Stotfield there are soft greenish-white sandstones containing 

 Ostrea Sowerbyi, Tancredia axiniformis, and Astarte hombordalisi, 

 and are probably near the base of the Bathonian Series. 



. E. CONTINENTAL EQUIVALENTS 



1. France 



The Middle Jurassic strata of the Parisian basin are a continua- 

 tion of the British Series, and their outcrop is almost continuous 

 round the basin, though concealed here and there beneath the 

 transgressive Cretaceous deposits. The districts where the succes- 

 sion is most clearly exposed are that of Bayeux and Caen in 



