62 



Feather stonhaugh'^s Geological Report. 



shells, and fresh-water marls. The term miocene is expressive 

 of an increased number of recent shells in its deposites, but 

 that they are in a minority as to numbers. 



The vpper tertiary or pliocene includes the tertiary beds of 

 Sicily, the crag of Norfolk and Suffolk, in England, and the 

 sub-Appenine marls. These last consist of various deposites 

 of marl, with sand abounding in fossil shells, of which upwards 

 of 40 per cent, belong to existing species. The crag is found 

 sometimes lying on the London clay, sometimes on the chalks 

 It is a sort of ancient beach, where sand, gravel, earth, red 

 ferruginous sand with ochreous nodules, and coarse white and 

 other sands, containing vast quantities of fossil shells, succeed 

 to each other. The proportion of recent shells is about the 

 same as that found in the sub-Appenine beds, and they are, 

 therefore, deemed to be of the same age. The tertiary beds of 

 Sicily consist of stratified marine deposites of clay, sand, and 

 limestone, at great heights above the sea, and which contain 

 95 per cent, of existing species. The term pliocene expresses 

 a majority of recent shells to be present. 



These tertiary beds, which occupy so large a portion of the 

 surface of Europe, are well developed in the United States, and 

 extend as far to the south as the country has been examined, 

 usually accompanying the subcretaceous beds, and covering 

 a prodigious area towards the Atlantic, south of the State 

 of New York. The vast deposites of tertiary shells in this 

 area are now, in situations where they are accessible, use- 

 fully applied to agricultural purposes, especially in New 

 Jersey, Maryland, and Virginia. The mineral character of 

 the deposites in which these fossils are found, is often formed 

 by various-colored clays of a very unctuous character, oc- 

 casionally divided by thin ferruginous seams, sometimes 

 abounding with minute crystals of selenite, at other times con- 

 taining very large aggregate crystals, all of which appear to 

 owe their origin to the organic bodies superincumbent to them. 

 Sometimes, as in the banks of the Choptank river, in Talbot 



