For criticisms, while the work was passing through the 

 press, my thanks are due to Professor W. 0. Crosby and to 

 Dr. R. T. Jackson. To Professor Irving P. Bishop of Buffalo, 

 special acknowledgements are due for the care and labor he 

 has gratuitously given to the preparation of the photo- 

 graphs from which the full page plates of Part I. are made. 

 Finally, to Dr. Lee H. Smith and the other members of the 

 publication committee, my thanks are due for the libera lit v 

 which they have shown in the number and character of the 

 illustrations. 



In conclusion it should be mentioned that a portion of 



this paper was prepared during the author's connection 



with the Massachusetts Institute of Technology, and that a 



series of the fossils described in Part II., is contained in the 



collection of that institution. Another series is to be found 



in the collections of the Buffalo Society of Natural Sciences. 



Other specimens, from which illustrations and descriptions 



were prepared, are contained in the Student Palaeontolo- 



gical collection at Harvard University. The types of the 



new species, unless otherwise noted, are in the author's 



collection. 



Harvard University, 



Cambridge, Mass., Feb. 12, 189s. 



