§25. 



THE LIAS. 521 



found, and that the strata were formed during alternate 

 subsidences and elevations of this part of Virginia. They 

 contain shells and fishes (TetragonGlepis, and a new 

 genus, Dictyopyge of Sir P. Egerton, Catopterus of Mr. 

 W. C. Redfield,*) related to European Liassic species. 

 Mr. Lyell regards this coal as of the age of the Inferior 

 Oolite and Lias : and if this opinion be correct, these 

 deposits are the first ascertained equivalents of any of the 

 oolitic series hitherto discovered in North America. 



25. The Lias. — The lowermost group of the Oolite 

 or Jurassic system termed the Lias, consists of stratified 

 blue and grey marls, clays, and limestones, amounting in 

 total thickness to from five hundred to one thousand feet, 

 and abounding in many peculiar fossils. The principal 

 lithological features are the uniform aspect, and distinctly 

 stratified character of the limestones and intervening argil- 

 laceous layers ; the most constant subdivisions are those 

 mentioned in the table, p. 493. 



It may be stated in general terms, that the Lias of 

 England extends along the western escarpment of the 

 Oolite, forming a district which presents an exceedingly 

 variable surface, occasioned by the disruption and subse- 

 quent denudations which the strata have undergone. The 

 course and extent of these deposits from Yorkshire to the 

 Dorsetshire coast, are admirably described by Mr. Cony- 

 beare,f from whose work the following abstract is derived. 



The Lias, from its northernmost limits on the Yorkshire 

 coast, where it underlies the strata of the eastern moor- 

 lands, passes to the south of Whitby and to the east of 

 York, and crosses the Humber, near the junction of the 

 Trent and Ouse ; stretching onward beneath the low oolitic 

 range of Lincolnshire, it extends to the Wold hills, on the 



* Geological Journal, vol. iii. PL VIII. 



f Outlines of the Geology of England and Wales, p. 261. 



