REPORT OX THE GEOLOGY OF NORTH AMERICA. 40 



not to omit the curious and important fact, in harmony, I believe, 

 with all the views here advanced, that among the organic re- 

 mains of these deposits no traces of anything of freshwater or 

 terrestrial origin have ever been discovered. 



Stepa in the History of the Tertiary Formations of the United 

 States. — The whole of that large tract of the Atlantic plain and 

 the basin of the Mississippi now found to be occupied by the 

 tertiary and cretaceous formations, was originallj- laid down by 

 M'CIure as alluvial. The first approach to a just knowledge of 

 its geology commenced with the determination of about fortj/^ 

 species of fossil shells collected in Maryland by Mr. Finch. 

 Neither of these gentlemen, however, drew any geological in- 

 ferences from the organic remains they examined. Dr. Van 

 Ransaellar afterwards i-eferred the deposits in question to the 

 age of the upper marine tertiary formation of England. Dr. 

 Morton supported the same opinion, pointing out several species 

 of fossil shells common to both sides of the Atlantic. After- 

 wards, in 1830, Mr. Conrad visited Maryland, discovered the 

 newer pleiocene at the mouth of the Potomac, which however he 

 did not pronounce to be tertiary, examined the fossils of the 

 formations which I have called middle tertiary or older pleiocene 

 and meiocene, and which he had previously named upper marine, 

 and also those of Fort Washington on the Potomac, which he 

 ventured to suggest were of the age of the London clay. In 

 1832, after a visit to Suffolk, James river, and York, to collect 

 tertiary shells, Mr. Conrad commenced his work on the fossil 

 shells of the tertiary formations of this country, retaining the 

 term ' upper marine ' for the older pleiocene, using the title 

 ' middle tertiary ' for what he had shown to belong to the age 

 of the London clay, and which he now shows to be our eocene, 

 and applying the name 'lower tertiary' to a class of beds de- 

 scribed as the plastic clay formation, first by Mr. Finch, and 

 afterwards by Hitchcock, and Morton, and as subordinate to the 

 secondary by Vanuxem, but which I have recently shown, under 

 the appellation of ' ancient alluvium', to be of much more recent 

 formation. Not long after, Mr. Conrad visited the eastern shore 

 of Maryland, where, on the Choptank, he procured many new 

 fossils, and made some interesting observations upon the beds 

 in which they occur. In 1833 he visited Alabama, where he 

 found the eocene very largely developed. His discoveries among 

 the organic remains of that quarter constitute the largest con- 

 tribution yet made to our tertiary geology. More recentlj^, my 

 brother and myself have begun the development of the pleiocene 

 and meiocene in Virginia. In 1834, Mr. Lea published his 

 Contributions to American Geoloqy, describing about two 



1834. E 



