viii PREFATORY NOTE 



Procamelus major (Leidy) appears to be a valid species, while the specific 

 identity of Procamelus mcdins and P. minor is not yet proven. The same may 

 perhaps be said of Mastodon floridanm, but until other specimens of Mastodon 

 serridens can be secured Mastodon floridanus should undoubtedly be con- 

 sidered as distinct. Hippotherium princeps, in the opinion of the writer, rests 

 on an abnormal tooth of Eqiius major. 



With the exception of the paragraphs on the tusks the most important 

 part of this memoir, that relating to Mastodon floridanits, was written by Dr. 

 Leidy, as was also most of the description of the three species of Procamelus. 

 The portions treating of Rhinoceros and Hippothcrinm were prepared by the 

 writer, whose initials are appended to these and to other parts for which he is 

 responsible. 



In view of the numerous and accurate illustrations prepared by Miss 

 Sinclair, which will furnish important and much-needed means of comparison 

 with other material, the descriptions have purposely been made brief. 



I am indebted to Professor Cope for the privilege of examining the types 

 of various species in his possession, and a considerable number of specimens 

 of Procamelus collected by the Geological Survey of Texas. 



FREDERIC A. LUCAS. 



WASHINGTON, D.C., 



June 30, 1894. 



