PREFACE 



The best place for this branch in the curriculum will 

 be as a preliminary study in the course on Dental Anat- 

 omy, preceding and leading up to human dental anat- 

 omy. It begins with the lowest form of life and leads up 

 to the highest in regular gradation, — taking the teeth 

 seriatim from the lowest types, and showing their pro- 

 gressive evolution from simple to complex forms. 



It would be impracticable to append references to au- 

 thorities in a condensed work of this character, for 

 economy of space; but the writer takes pleasure in ac- 

 knowledging his indebtedness to the leading authorities 

 upon odontography and zoology for the many drafts he 

 has made upon the rich stores they have accumulated 

 and placed at the disposal of students and teachers. 

 He wishes also to acknowledge the courtesy of Mr. C. H. 

 Ward, of Ward's Natural History Establishment, Roch- 

 ester, N. Y., who kindly furnished specimens for most 

 of the illustrations. 



A. H. Thompson. 



Topeka, Kansas. 



