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NEW YORK STATE MUSEUM 



Clinton counties which have now been so fruitful in setting forth 

 with clearness the relations and extent of the lower formations. 

 Somewhat earlier than this Professors Brainerd and Seely of Mid- 

 dlebury College, Vermont, had exhumed and R. P. Whitfield had 

 described the rich fauna of the Beekmantown formation at Fort 

 Cassin Vt. and this work gave a new impetus to investigations of 

 the faunas on the New York side of the Lake Champlain basin. 

 During the period from 1890 onward., collecting was done here for 

 the State Museum in a desultory way by Dr Carl Rominger and 

 Jacob Van Deloo but it was not until 1899 that the acquisition of 

 fossils was taken up seriously by the State Paleontologist. At that 

 time Mr Gilbert van Ingen entered the field, carrying on operations 

 in a systematic and refined manner. He was thereupon joined 

 by Dr Ruedemann who has since continued the work alone. The 

 result of these operations for several seasons has been the acquisi- 

 tion of very extensive collections upon which the present work is 

 chiefly based. Meanwhile some writings have appeared which bear 

 upon the composition of these faunas ; we may note especially a 

 recent paper issued in the Report of the State Paleontologist for 

 I 9°3 by Prof. George H. Hudson on Chazy fossils from Valcour 

 island and a treatise on the trilobites of these rocks by Percv E. 

 Raymond. The present work deals exclusively with the cephalo- 

 pod fauna of the Beekmantown and Chazy formations of the Cham- 

 plain valley. The study of these objects involves peculiar difficulties, 

 their preservation is not always good, the determinations of their 

 organic relations have been rendered somewhat complicated by 

 recent labors on fossil cephalopods and yet being the most highly 

 organized mollusca at this period of the earth's history and of 

 primary importance in determining the stratigraphic values of the 

 formations concerned, the unraveling of their ontogeny and genetic 

 relations constitutes a definite advance in New York paleontology. 



In the preparation of this work the author has received utmost 

 consideration from coworkers in this field and makes acknowledg- 

 ment especially to Prof. H. M. Seely of Middlebury College, 

 Prof. G. H. Perkins of Burlington I niversity and Prof. G. H. 

 Hudson of Plattsburg, to Dr J. F. Whiteaves of Ottawa, Dr F. D. 

 Adams of Montreal and Prof. R. P. Whitfield of New York for 

 the opportunity to consult the collections in their charge, and to 

 Dr F. W. Sardeson of Minneapolis and Mr R. S. Bassler of 

 W ashington for the loan of specimens. 



John M. Clarke 



State Paleontologist 



