4 MONOGRAPH OF DURA DEN. 



times ; whose families have become utterly extinct amidst 

 revolutions and convulsions by which sea and land have inter- 

 changed places, and whereby the physical aspects of all around 

 have been modified or produced ; and now entombed in their 

 marble sepulchres — 



" Sand liath fill'd up their palaces of old, 

 Sea-weed o'ergrown their halls of revelry." 



The arrangement proposed to be followed in this Memoir will 

 comprise, — 



I. A general topographical description of the district. 



II. The geological position of the yellow sandstone, and its 

 relations to the Primary, Devonian, and Carboniferous systems. 



III. History of the fossil remains. 



IV. Descriptions of the fossil remains and their remarkable 

 characteristics. 



V. General inferences as to the conditions of the primeval 

 seas ; earliest appearances of vegetable and animal life ; the 

 great fish epoch in the Devonian period ; causes of extinction ; 

 the igneous and trap formations and disturbances ; and the 

 subsequent vast development of the carboniferous flora in the 

 production of coal, ironstone, and limestone. 



