PREFACE vil 



animals which will not only be of aid to the instructor in locating 

 material but will serve as a starting point for special survey 

 work by the interested student. 



The senior author particularly wishes to acknowledge his 

 indebtedness for suggestions by W. L. Chandler, Laurene Krogh, 

 Gerard Dickman, and Nordahl Peterson, former student assist- 

 ants who were associated with him in presenting this course. 

 The efficient services of Miss Grace E. Jones in preparing, re- 

 drawing, and arranging illustrations also deserve special mention. 

 To the various publishers and authors who have granted ready 

 permission to use illustrations, thanks are due. 



The Authors. 

 Minneapolis, Minn. 

 January, 1930 



