320 ARMADILLOS. 



development(l). Each denticle is developed according to the same 

 laws, and by as simple a matrix, as those larger teeth in other 

 Mammalia which consist only of dentine and cement. The dentine 

 is formed by the centripetal calcification of the pulp, and the 

 cement by ossification of the capsule : both pulp and capsule con- 

 tinue to be reproduced at the bottom of the alveolus, pari passu 

 with the attrition of the exposed crown ; and the mode and time 

 of growth being alike in each denticle, the whole compound tooth 

 is maintained throughout the life of the animal. The augmentation 

 in the size of the whole tooth, during the growth of the jaw, is 

 effected by the development of new denticles, and a slight increase 

 of size in the old ones, at the base of the growing tooth, which 

 in the progress of attrition and growth, becomes its grinding surface. 



ARMADILLOS. 



136. It has been a subject of regret to most Naturalists that 

 the great Reformer of Zoology should have substituted the name 

 Edentata for that of Bruta, applied by Linnaeus to the order of 

 Mammals which he had characterized by the absence of incisors. 

 The subsequent discoveries of Naturalists have much augmented 

 the Edentata of Cuvier, and have shown that out of the great 

 number of species contained in this order, two only are without 

 teeth, whilst almost all are destitute of incisors. The exceptions 

 to the Linnaean character occur in the family of Armadillos, in 

 which the species of the existing subgenus Euphractus, and of the 

 extinct genera Glyptodon and Chlamydotherium have teeth in the inter- 

 maxillary bones. 



(1) M. Fred. Cuvier, at the close of his description of the teeth of the Orycterope 

 remarks : " Les machelieres de I'orycterope ont une structure qui leur est tout-a-fait par- 

 ticuliere ; leurs racines ne diflFerent point de leur couronne, mais elles ne presentent point 

 de cavite pour la capsule dentaire, comme font toutes les especes de dents chez les mam- 

 miferes; elles semblent presenter un nouveau mode de developpement pour ces organes. 

 Comme toutes les dents depourvues de racines proprement dites, elles paraissent croitre 

 constamment; mais, au lieu d'etre formees de couches successives et toujours renaissantes, 

 elles le sont, en apparence du moins, de fibres longitudinales, pentagones, et dent le centre 

 serait perce, ou rempli d'une substance de couleur plus foncee que ces fibres." Dents de 

 Mammiferes, p. 200. 



The present knowledge of the dental system of the Orycterope strikingly exemplifies the 

 manner in which anomalies disappear as we gain a deeper insight into structure. 



