PREFACE. 



In Mr. Maclure's " Geology of the United States," the formation we are 

 about to examine is called alluvial, without any specific reference to the 

 contained fossils, which at the time that work was published, were almost 

 unknown : several of them were subsequently described by Mr. Say, who, 

 however, took little notice of their geological relations. 



Dr. Harlan has written several papers on the Marl of New Jersey, with 

 particular reference to fossil osteology; and Dr. Dekay has more recently 

 pursued the same interesting investigation. 



Mr. Vanuxem's memoir on the Secondary, Tertiary and Alluvial forma- 

 tions of the United States, embraces brief, but important views of the are- 

 naceous deposit of this Synopsis, which he was the first to identify with 

 the Chalk series of Europe, although he does not refer it to any particular 

 division of the Chalk. 



With these and other aids, all of which will be more specifically ac- 

 knowledged hereafter, I applied myself to the study of what has been 

 termed the " Marl region" of this country ; and my object was greatly pro- 

 moted by the extensive excavations at the Chesapeake and Delaware canal. 

 I have also had access to nearly all the public and private collections of 

 which marl fossils form a part ; and in this respect owe much to the kind- 

 ness of my friends Dr. Blanding, Mr. J. P. Wetherill, Mr. Nuttall, Prof. 

 Hitchcock, Mr. Cooper, Dr. Dekay, Dr. Z. Pitcher and Mr. T. A. Conrad. 

 The last named gentleman, although he has not written on this portion of 

 American geology, has contributed as much as any one to its elucidation ; 

 and to him also belongs the honour of first identifying and making known 

 the Calcaire grossier, or Eocene, of Alabama. 



The first edition of this Synopsis was read before the Academy of Natu- 

 ral Sciences of Philadelphia, in the autumn of 1829, and published in 



