XX.] ANTERIOR AND POSTERIOR EXTREMITY. 339 



There can be no question but that the carpus and tarsus, 

 the metacarpus and metatarsus, and the various digits 

 beginning at the pollex in the one, and the hallux in the 

 other, are really homologous ; the circumstance of the con- 

 stant absence of one of the bones of the preaxial digit in 

 both fore and hind limbs is most significant. 



In the carpus and tarsus, the serial homology of the four 

 bones of the distal row in their respective order is generally 

 admitted, but with the other bones there is still some differ- 

 ence of opinion. Gegenbaur has, however, given good 

 reasons,^ derived chiefly from the results of tracing both 

 limbs back to their less modified condition in Reptiles and 

 Amphibia, for considering the astragalus as equivalent to 

 the scaphoid and lunar united, or the scapho-lunar bone of 

 the Carnivora &c. ; the calcaneum as representing the 

 cuneiform, and not, as often supposed, the cuneiform and 

 the pisiform (the latter being only a sesamoid) ; and the 

 navicular of the foot as representing the os centrale, found 

 only occasionally in the manus of Mammals. 



^ " Untersuchungen zur Vergleiclienden Anatomic,'' i*" Heft, Carpus 

 und Tarsus, 1S64. 



