28 THE PLIOCENE AND PLEISTOCENE DEPOSITS OE MAEYLAND 



Four years later Vanuxem and Morton undertook a more detailed 

 division of the Coastal Plain deposits. They distinguished four horizons 

 which they called Secondary, Tertiary, Ancient Alluvial, and Modern 

 Alluvial. Their descriptions are vague and as few localities are given, 

 it is difficult to understand exactly what limits they intended to give to 

 their various deposits. However, it is quite certain that their Ancient 

 and Modern Alluvial was intended to embrace, at least in part, what is 

 to-day known as Lafayette, Columbia, and Eecent. This conclusion is 

 borne out by the significant statement made by them that " bones of the 

 mammoth, and other mammiferous terrene quadrupeds found in this 

 region, belong to the two Alluvials." 



In 1830 Conrad began the publication of his interesting and important 

 series of papers on the organic remains of the Maryland Coastal Plain. 

 In the first one of these he called attention to the " diluvial " deposit 

 of sand and gravel which covers the peninsulas of Maryland and excludes 

 from view the underlying formations except where they are exposed in 

 ravines. He made no attempt to sub-divide this " diluvial," but was 

 attracted by the fossil horizons at Wailes Bluff near Cornfield Harbor, 

 which he apparently thought distinct in age from the overlying gravels. 

 Conrad's account of this section was so accurate that there is no difficulty 

 in recognizing the locality and little need be added to his original de- 

 scription. He made a sharp distinction between the fossil-bearing clays 

 below and the unfossiliferous cross-bedded gravel and sand above. He 

 also drew attention to the fact that the fossils had a very recent aspect 

 and many of them were identical with living forms inhabiting the 

 shore of the United States, and as they were " sub-fossilized," they 

 resembled some of the more recent formations of the West Indies. Two 

 years later Conrad made an attempt to sub-divide the surficial deposits 

 which he had previously designated by the general term " diluvial." 

 He separated them into " Diluvium" which he described as composed of 

 sand, clay, and rounded fragments of rock containing remains of large 

 quadrupeds and deposited without order or arrangement by violent 

 currents. He correlated it with the Gravier coquillier or Crag. The 

 more modern aspects of the surficial cover he called " Alluvial " and 



