170 



ANATOMY OF VERTEBRATES. 



53, is more expanded at its proximal end than in the Crocodile or 

 Lizard ; the inner (ulnar) tuberosity is more prominent, the radial 

 crest much more developed : with a base coextensive with one 

 fifth of the shaft of the bone, it extends in a greater proportion 

 from the shaft, affording a powerfid lever to the muscles inserted 

 into it. The articular head is reniform. The shaft is cylindrical : 





Stuk-ton ol Ptirmlacliilus cm 



(.s?/-(^\ A. Restonition of Pterod:icty!e. CLXXX. 



the walls thin and compact, the cavity large, and was filled with 

 air as in birds of flight.' 



The ' pneumatic foramen,' or that by which the air passed from 

 a contiguous air-cell into the bone, is situated on the fore (palmar) 

 side, a little below the radial end of the head of the bone. The 

 radius, ib. 54, and ulna, ib. 55, are very long, straight, and closely 

 connected together. The digits show the lacertian number of 



> CXLix. p. 16. iLXTi. p. 451. This tliscovei-y breaks down the following 

 distinction : ' Au ruslc, on distingue tonjours riinmoi us d'un Kzaid do celui d'uii 

 oiscau, p.arcecpic le premier n'est pas crcnx ni perco dc trous pour rentrce de I'air 

 dans son interieur.' CLi. v. pt. 2, p. 296. 



