ENAMEL IN THE TEETH OF AN EMBRYO EDENTATE 

 (DASYPUS NOVEMCINCTUS LINN)/ 



BY 



A. M. SPURGIN, M. D. 

 With 2 Plates. 



Tomes was the first to work on the embryology of the teeth of the 

 nine-banded armadillo {Dasypus novemcinctus L.). In 1874, he exam- 

 ined two embryos, one early and one relatively late. The exact length 

 of these embryos I have been unable to ascertain, but in the early one 

 a layer of dentine had been deposited. He said that the stellate reticu- 

 lum or enamel pulp was absent, and that he failed to find any enamel or 

 anything like it upon the teeth. He regarded the enamel organ as rudi- 

 mentary, stating that an enamel organ was present in all tooth-germs, 

 and that it was entirely independent of any subsequent development of 

 enamel. 



In 1884, Pouchet and Chabry examined embryos of Oryderopus capen- 

 sis, and Bradypus tridactylus. In an embryo of the former, of 32 cm., 

 they found a typical rudimentary incisor with an enamel organ and 

 dental papilla in which a layer of dentine had been deposited. An embryo 

 of 12 cm. of Bradypus tridactylus showed an enamel organ covering the 

 dental papilla in which a layer of dentine had appeared. In an embryo 

 of the same animal of 23 cm. in which the teeth had erupted, they 

 described the dentine, vasodentine, and outer coat of cement of the 

 typical adult tooth. They found no enamel, and state that the stellate 

 reticulum was absent in the enamel organ of the sloths. 



As early as 1828, A. Brants found a rudimentary incisor in the lower 

 jaw of Bradypus tridactylus. P. Gervais in 1873 confirmed this dis- 

 covery. Burmeister made a similar discovery in the fossil Scelidotherium 

 leptocephaluni. Flower, in 1869, described a rudimentary incisor in the 

 lower jaw of Tatusia Peha (Dasypus novemcinctus) , and in 1877 Eein- 

 hardt observed as many as four in the lower jaw of the same animal. 



Hensel has shown that the armadillos, Dasypus novemcinctus and 

 D. hybridus Desm. are diphyodont. In an examination of thirty five skulls 



I Contributions from the Zoological Laboratory of the University of Texas. No. 51. 

 American Journal of Anatomy. — Vol. III. 



