586 



THE BOX TORTOISES OF NORTH AMERICA— TAYLOR. vol.xvii. 



reference to the number of phalanges in each hind foot the species 

 are as follows : T. major and T. Carolina, 2-3-3-3-2, the same number 

 as in the forefoot; T. ornata and T. mexicana, 2-3-3-3-1 ; T. hauri and T. 

 triunguis, 2-3-3-2-1. 



The loss of the phalanges on the hind foot might be accounted for by 

 supposing that the distal phalange does not develop. But iu the case 

 of the fore foot, where the full number of claws are still present, the 

 distal ijhalange evidently does not disappear. Hence the reduction 



Figs. 2-7. 



SKULLS OP TEKBAPENE. 



Showing modification of the zygomatic arch in different species. 



a, Postfrontal. b, Quadrato-jugal. c, Jugal. 



( For explanation of figures see page 585. ) 



must take place either by the coossification of two phalanges, or a 

 phalange and a metacarpal, or by the disappearance of a phalange. 



Zehntner, 1890, after studying the development of the Alpine Swift, 

 Cijpselus melha, concludes that the reduction in the number of pha- 

 langes takes place in this species by coossification. He states that in 

 the fourth digit the first phalange probably unites with the fQurtb 

 metatarsal, while the third and fourth phalanges unite with each other. 



