378 MR. w. H. FLOWER ON THE [June 11, 



The following papers were read : — 



1. On the Development and Succession of the Teeth in the 

 Armadillos [Dasyjjodida) . By "William Henry Flower, 

 F.E.S. &c,, Conservator of the Museum of the Royal 

 College of Siu'geons. 



With one exception, all writers on the dentition of the Arma- 

 dillos, 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 suc- 

 cession*, or have assigned these animals, with the rest of the Eden- 

 tata, to the section of mammals termed " monophjodont," or those 

 that generate a single set of teethf. The exception I allude to is 

 Professor Gervais, who, in his ' Histoire naturelle des Mammif eres ' 

 (1855, vol. ii. p. 252), makes the following observation, accompa- 

 nied 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 

 et 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 Mammif eres. 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 eu bas, sont 

 moins arrondies que celles de la seconde dentition, et leur raciue 

 se dcdouble en un chevron, dont les deux branches peuvent se se- 

 parer I'une de 1' autre par suite de I'usure de la partie coronale. Les 

 dents de remplacemeut poussent immediatement au-dessous de celles 

 de lait, qu'elles chassent comme des coins, en se pla9ant eutrc les 

 deux branches de leur racine. C'est un mode de remplacement bieu 

 plus semblable a celui des Crocodiles qu'a celui des Mammif eres 

 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 suc- 

 cessive 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. 001 ; Anat. of 

 Vertebrates, vol. ii. p. 278 (1SG6). 



