PREFACE xi 



York; Colonel Thomas L. Casey, United States Engineer Corps; Mr. Edgar 

 A. Smith, of the British Museum, and M. Maurice Cossmann, of Paris. 



Dr. J. C. McConnell, of Washington, D. C, who has supplied the admirable 

 pen drawings which are reproduced in the illustrations, has been an indispen- 

 sable collaborator. When the plates of this work are compared with the muddy 

 and often wholly worthless heliotypes which disfigure so many pretentious 

 modern paleontological publications, both the author, the Institute, and the 

 student must feel that they are entitled to congratulate themselves on the 

 quality of Dr. McConnell's work, which is certainly unequalled in America, if 

 not in the world. 



William Healey Dall. 



Smithsonian Institution, Washington, D. C, March 31, 1903. 



