150 



On the Tarsus and Carpus of Birds. 



It surely is not the distal end of the fibula, for in the 

 larger specimen of tibia examined (fig. 4) I find, with the 

 aid of a hand lens, a delicate tendinous thread running from 

 the lower end^ of the fibula and the upper end of the pre- 

 tibial bone, and passing each other, showing no sign of ap- 

 proximation. Furthermore, in all the embryo birds I have 

 thus far examined (see plate iv), the fibula shows no signs of 

 torsion. Dismissing the idea that it represents a third bone 

 of the leg, "as contrary to all analogy," we have 

 only to admit that it represents a new tarsal bone 

 of the proximal series. 



The specimen represented in figure 1, was 

 sent to me by Prof. WN'man sometime before 

 he had examined the other bones with reference 

 to this new tarsal. In this specimen the meta- 

 tarsals are still separate, and the presence of 

 the three tarsal bones thus far described is but 

 dimly made out ; yet the pretibial bone is quite 

 distinct, and of much importance is the fact that 

 its lower edge is below the lower edge of the tibia. Satisfied 

 that it is a true tarsal bone, to what bone in the tarsus shall 

 we compare it? 



After studying over it very carefully, and comparing it 

 with figures of certain amphibians, given by Gegenbaur, and 

 with some of my own drawings of the tarsus of the com- 

 mon wood salamander, PJethodon.erylhronotns, I believe it 

 to represent the intermedium of Gegenbaur. In the tarsus 

 of Salamandra maculosa, as given by Gegenbaur, the inter- 

 medium is represented as a much elongated bone, broader at 

 the bottom, and wedged between the tibia and fibula, half 

 of it being actually above the distal margins of these two 

 bones. Above the reptiies, the intermedium is supposed by 

 Gegenbaur to coalesce with the tibiale or astragalus. 



In other words the astragalus represents the intermedium 

 and tibiale, connate. Gegenbaur believes that the astraga- 

 lus represents the scaphoid and lunare of the carpus. In 



Fig. 5. 



