JURASSIC PERIOD. 447 



and extending across England, north of northwest, to the river 

 Humber, and still farther north, on the eastern coast of Yorkshire, 

 almost to the mouth of the Tees. They thus cover eastern 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 appa- 

 rent 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 surround- 

 ing 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 Eng- 

 land, 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 "Wurteniberg 

 and Bavaria in southern 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 north- 

 ern 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 

 referred to) ; (2) the epoch of the Oolite, or the Oolitic (No. 7 b), so 

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

 (seep. 85) ; 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 Liassic beds consist mainly of grayish limestones, containing 

 marine fossils. 



The Oolitic include other limestones, part of which are oolitic in 

 texture, along with arenaceous and clayey strata in many alterna- 

 tions. 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. 



