THE PKE-ADAMITE EARTH. 



which existed severally during the ten. periods of the Jurassic 

 age, their remains being deposited in the ten superposed stages 

 which compose the Jurassic formation. 



3rd. That each period, therefore, had its own special fauna, 

 having nothing in common with the preceding or succeeding 

 period. 



4th. That the specifli which, owing to accidental causes or 

 erroneous designations, have been found in two or more stages, 

 the number of which has been greatly overrated, do not in 

 reality exceed 1| per cent, of the total number of species dis- 

 covered.* 



326. The geography of Europe in the Jurassic age has been 

 traced and mapped with considerable precision by Messrs. Elie de 

 Beaumont and D'Orbigny. The Jurassic formation, which has 

 been well observed, and its limits determined, shows the 'extent 

 and configuration of the seas, and consequently the outlines of 

 the land. The Jurassic seas in Western Europe formed three 

 principal basins, extending over certain parts of France and the 

 eastern and southern parts of England. The form and limits of 

 these are shown on the map (fig. 153), drawn by M. D'Orbigny, 

 here reproduced with the permission of the author and publisher, 

 which does not differ in any essential points from that of M. Elie 

 de Beaumont (fig. 154), as will presently appear. 



327. The Anglo-Parisian basin covering the north-west of 

 France and the eastern division of England, was limited in 

 England by a line directed N.N.E. from Somersetshire to Durham, 

 passing therefore through the counties of Gloucester, Worcester, 

 Stafford, Derby, and York ; all that part of England to the east 

 of this line being then covered by the sea. 



On the other side of the Channel, the western shores of this 

 basin passed across Normandy from St. Lo southwards to Angers 

 on the Loire. It skirted the northern limit of the central plateau 

 from Angouleme to Autun. On the north its shores were directed 

 from Calais by Arras to Metz and Yerdun, where they turned 

 southwards to Chaumont. This basin communicated with the other 

 two by two straits, one of which extended from La Rochelle to the 

 eastern part of Angouleme, marked in the map as the Breton 

 Strait, and the other from Chaumont to Autun, marked as the 

 Belgi- Yosgian Strait. All that part of the channel east of Devon- 

 shire constituted part of this Anglo-Parisian basin or sea. The 

 entire province of Brittany in France was at this epoch dry land. 



328. The Pyrenean basin was limited on the north by the 

 Breton Strait, and on the north-east by the central plateau, 



* D'Orbigny, Paleontologie, vol. ii. p. 426. 

 70 



