ARTICLE IX. 
CONTRIBUTIONS TO A REVISION OF THE NORTH AMERICAN BEAVERS, 
OTTERS AND FISHERS. 
(Plates XXI-XXV.) 
BY SAMUEL N. RHOADS. 
Read before the American Philosophical Society, May 6, 1898. 
An unusually fine series of the skins and skulls, with reliable data and measure- 
ments, of the beavers, otters and fishers of the United States and Canada having lately 
come into the custody of the writer, it is thought advisable to publish the results of a 
study of the various nominal forms of these mammals and briefly discuss the nomencla- 
ture involved. Owing to a lack of specimens from some regions whose faunal condi- 
tions are known to produce in many other mammals well-recognized geographic varia- 
tions, this paper must be considered rather as a contribution to the subject, and in no 
sense a complete synopsis. The area covered by this study comprises solely that part of 
North America north of Mexico, no attempt being made to discuss the relationships of 
the tropical species. 
To Mr. Outram Bangs the author acknowledges his gratitude for a most valuable 
loan of skins and skulls of nearly every species and race recorded in these pages. To 
the kindness of Mr. F. W. True, of the National Museum, is due the loan of a series of 
skulls of the Alaskan otter. 
The North Carolina Department of Agriculture has courteously loaned two skins 
and four skulls of beavers recently killed in Stokes county of that State through the 
kind offices of Mr. H. H. Brimley, the Curator of the State Museum. 
Aid has likewise been generously given by Dr. J. A. Allen, Dr. C. Hart Merriam, 
Dr. T. 8. Palmer, Mr. Gerrit S. Miller, Jr., Dr. M. W. Raub and Mr. C. 8. Brimley. 
THE BEAVERS OF NORTH AMERICA. 
Contrary to evidence which must eventually be accepted by all zodlogists, the Ameri- 
can beaver, Castor canadensis Kuhl, is still considered by many eminent authorities as 
