434 MESOZOIC TIME. 



the mouth of the Tees. The Jurassic seas appear to have covered 

 the eastern part of England ; while the western part, from the north 

 to Cornwall, was apparently an elevated barrier against the ocean. 

 Jurassic beds also occur on the northeast coast of Ireland, as at the 

 Giants' Causeway and on the Western Isles. 



Following the line of the British Jurassic belt from Lyme-Regis 

 and Portland across the English Channel, we come upon an apparent 

 continuation of the belt in France. It sweeps south, by the borders 

 of Brittany, to the central plateau of France, and then east and north, 

 by the eastern boundary of the empire, thus surrounding a large area 

 of which Paris is the centre. 



The line of barrier-islands of western England is continued in Brittany, in western 

 France; the line of the outcropping Jurassic, in similar outcropping Jurassic in France; 

 and the area of the shallow Jurassic sea over eastern England, in the extensive Parisian 

 basin, — a sea which was then the western and southern border of the German Ocean, 

 and covered what are now the sites of London and Paris. 



The central plateau of France — a region of crystalline rocks — is nearly encircled by 

 Jurassic strata; and the rocks are continued eastward over the Jura Mountains (by 

 Neufchatel), and along their continuation through Wurtemberg and Bavaria in south- 

 ern Germany. They appear also in northern Germany (Westphalia) and the Alps 

 (Savoy, etc.). 



Jurassic beds occur also along the Andes in many regions, from their northern limit 

 to Tierra del Fuego. They are found in many parts of Asia, and have been recognized 

 by W. B. Clarke in Australia. 



The Jurassic period, in England and Europe, is divided into three 

 epochs: (1) the epoch of the Lias, or the Liassic, so designated from 

 a provincial name of the rocks in England (No. 7 a on the map re- 

 ferred to) ; (2) the epoch of the Oolyte, or the Oolytic (No. 7 b), so 

 called because a prominent rock of the series in England is oolyte 

 (see p. 86) ; and (3) the epoch of the Wealden (No. 8 on map), named 

 from a region called The Weald, in Kent, Surrey, and Sussex, where 

 the beds were first studied. The Wealden are transition beds between 

 the Jurassic and Cretaceous, and are often referred to the latter, al- 

 though more closely related physically to the upper part of the former 

 period. 



The Liassic beds consist mainly of grayish limestones, containing 

 marine fossils. 



The Oolytic include limestones, part of which are oolitic in texture, 

 and others arenaceous and clayey. One of the limestones is a coral- 

 reef rock. All of the beds are of marine or sea-shore origin, as the 

 fossils show, excepting strata in the local Purbeck beds near the top 

 of the series, one of which, on the island of Portland, is called the 

 Portland dirt-bed. 



The Wealden is wholly of estuary or fresh-water origin ; the beds 

 consist of clays, sands, and, to a small extent, fresh-water limestone. 



