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Show 378 MR. W. H. FLOWER ON THE [Junell, The following papers were read :- 1. On the Development and Succession of the Teeth in the Armadillos (Dasypodidce). B y W I L L I A M H E N R Y F L O W E R, F.R.S. & c , Conservator of the M u s e u m of the Royal College of Surgeons. With one exception, all writers on the dentition of the Armadillos, whose works I have been able to consult, have either contented themselves with describing the teeth found in full-grown specimens, passing over in silence the question of their development and succession*, or have assigned these animals, with the rest of the Edentata, to the section of mammals termed " monophyodont," or those that generate a single set of teethf. The exception I allude to is Professor Gervais, who, in his ' Histoire naturelle des Mammiferes' (1855, vol. ii. p. 252), makes the following observation, accompanied by a figure of the specimen described :- " Leurs machoires, qui sont greles et plus ou moins allongees, sont toujours garnies de dents, mais ces dents varient pour la forme ct pour le nombre, suivant les differents genres. J'ai pu constater leur mode de remplacement, dont aucun auteur n'avait encore parle, et qui differe beaucoup de celui des autres Mammiferes. Dans le Cachicame, le seul Tatou que j'aie encore observe sous ce rapport, les molaires de lait, qui sont au nombre de sept en haut et en bas, sont moins arrondies que celles de la seconde dentition, et leur racine se dedouble en un chevron, dont les deux branches peuvent se se-parer l'une de l'autre par suite de l'usure de la partie coronale. Les dents de remplacement poussent immediatement au-dessous de celles de lait, qu'elles chassent comme des coins, en se placant entre les deux branches de leur racine. C'est un mode de remplacement bien plus semblable a celui des Crocodiles qu'a celui des Mammiferes heterodontes." As this observation has an important bearing upon the general principles laid down in all attempts to reduce the laws of the succession of mammalian teeth to a symmetrical and harmonious system, and has hitherto received very little, if any, attention from subsequent writers, I thought it desirable to investigate the subject afresh, and, if possible, set at rest any doubts which might exist regarding it. Fortunately, I have been able to examine the early dentition of a sufficient number of animals, of the same species as that referred to by Professor Gervais, the common Nine-banded Armadillo (Tatusia peba, Desm.), fully to confirm his observation, and to supply some further details towards the completion of our knowledge of the successive stages of the process of dental development in this animal. * Eapp, in his well-known monograph on the Edentata (1843), says, "Ueber einen Zahnwechsel ist mir bei den Edentaten nichts bekannt" (p. 52). t Owen, Cyclop, of Anat. and Phys. (art. Teeth) vol. iv. p. 901; Anat. of Vertebrates, vol. ii. p. 278 (1800). |
