TOOTH DEVELOPMENT IN DASYPUS NOVEMCINCTUS 



BERTHA E. MARTIN 

 From the Department of Zoology, Universiiy of Chicago 



FIFTEEN TEXT FIGURES AND FOUR PLATES 



A. Introduction 647 



B. Description of teeth in post-embryonic skulls 649 



C. Number of tooth germs present in the embryo 651 



1. Number of tooth germs in the embryonic lower jaw 651 



2. Number of tooth germs in the embryonic upper jaw 655 



D. Development of the functional back teeth 656 



1 . History and functions of the enamel organ 656 



2. History of the tooth cusps 660 



a. History of the cusps in the lower jaw 660 



b. History of the cusps in the upper jaw 663 



3. Secondary tooth buds , 663 



E. Development of the non-functional front teeth of the lower jaw 664 



1 . Discussion 670 



F. Development of tooth vestiges in the premaxilla 673 



1 . Discussion 676 



G. Summary 679 



A. INTR(3DUCTI0N 



Much interest has been attached to the development of teeth 

 in the armadillo since 1874 when Tomes first described an enamel 

 organ in the lower jaw of an embryo of Dasypus novemcinctus. 

 The teeth had always been described as possessing no trace of 

 enamel, and therefore the discovery of an enamel organ was re- 

 ceived with much surprise. Between the years 1891 and 1895 

 interest was kindled anew by a series of papers on the subject 

 by Rose, Leche, Ballowitz, and Kiikenthal. In 1904, Spurgin, 

 at the University of Texas, also worked upon tooth development 

 in this form. These investigators added much to our knowledge 

 of the subject, and for the most part their observations were cor- 

 rect. But many questions remained unanswered owing to the 

 fact that none of these investigators possessed a series of embryos 



647 



