XX.] ANTERIOR AND POSTERIOR EXTREMITY. 373 



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

 the metacarpus and metatarsus, and the various dibits 

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

 other, are serially homologous, or rather homodynamous ; 

 the circumstance of the constant absence of one of the 

 bones of the pre-axial 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, 1 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 ca'.caneum as repre- 

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

 cuneiform and the pisiform ; and the navicular of the foot 

 as representing the os centrale, found only occasionally 

 in the manus of Mammals. 



1 " Untcrsuchungcn zur vergleichenden Anatomic," l tcs Heft, 

 Carpus und Tarsus, 1864. For a modification of this view see Baur's 

 suggestion on p. 340. 



