418 SPECIAL GEOLOGY. 



lias in England, France, and Germany, is an alternation of 

 thin beds of limestone, with a light brown weathered surface, 

 separated by dark-coloured narrow argillaceous partings, so 

 that the quarries of this rock, at a distance, assume a striped 

 and riband-like appearance.* 



GEOGRAPHICAL DISTRIBUTION. The lias, like the oolite, 

 forms a belt which extends across our island, from its south- 

 western to its north-eastern shores, from Lyrne-Begis, in 

 Dorsetshire, to the north of Whitby, where it is lost beneath 

 the moorlands of the Yorkshire coast. It accompanies 

 the oolite with considerable regularity, from Lyme-E-egis 

 through Dorsetshire and Somersetshire to Gloucestershire, 

 in which county, about six miles south of Gloucester, 

 its western portion diverges still farther to the west, 

 and pursues a tortuous and intricate course, among the 

 counties of Somerset, Gloucester, Monmouth, and Gla- 

 morgan, attended with outlying portions and detached 

 masses. Its eastern portion continues a regular track 

 through parts of Gloucestershire, "Worcestershire, Warwick- 

 shire, Leicestershire, Lincolnshire, and Nottinghamshire, 

 into Yorkshire. 



On the continent, this formation is largely developed, in 

 the north and south-east of Prance, in Switzerland, and 

 Germany. In some countries, as in America, it is wanting 

 over extensiye areas. 



No part of the world has yielded organic remains of such 

 an interest Lag character as those which have been brought to 

 light in this country, an unrivalled collection of which con- 

 stitutes an important feature in the assemblage of organic 

 remains contained in the mineral-galleries of the British 

 Museum. 



In Gloucestershire the lias admits of a fourfold division, 

 into 



1 . Upper lias shales ; 2. Lias marlstone ; 



3. Lower lias shales ; 4. Lias limestone. 



The upper shales are seldom well exposed in the 

 escarpments of the Cotteswolds, but are seen in situ in the 

 liasic outliers of Dumbleton and Alderton, reposing on beds 

 of marlstone, which in these localities are extremely rich 



* Geology of England and Wales, page 261. 



