6 PREFACE. 



this was not present, they have been abridged, some- 

 times almost without change of language, from some pre- 

 vious writer. 



Trusting that this little volume may be a help and a 

 guide to others in the study of these animals, the author 

 presents it, and asks for it a lenient criticism; for none 

 more than he will probably ever realize its imperfections. 



Ann Arbor, May 17, 1876. 



