The Anatomy of Birds 10 



The tibia is much the larger bone of the lower leg, the fibula being flat and splint- 

 like in character, never quite reaching the lower end of the tibia and commonly 

 not extending more than two thirds of its length. The length of the tibia is 

 related to a bird's habits, being longest in wading birds, coming next in runners, 

 and of considerable development in 

 swimming birds. 



The foot of a bird never contains dpx 



more than four toes, and there may be 

 but two, as in the Ostrich, while the 

 three principal metatarsal bones are 

 united into one, with which the second 

 row of tarsal bones is fused, this form- 

 ing the tarsometatarsus, or, as it 



is 



atb 



p.pm 



par 



Fie 



ant.b.f 



15. Skull of Rhea, ventral view. 

 Pycraft.) 



(After 



p.pmx, palatine process; par, parasphenoidal rostrum; 

 v, vomer; pa, palatine; pt, pterygoid; bt.p, basipterygoid; 

 p.p, paraoccipital; ant.b.f, anterior basioccipital fonta- 

 nelle; mxp, premaxillary-palatine process. 



FIG. 1 6. Skull of Ptilotis. (After Parker.) 



p.px, palatal process of premaxillary; pr.pa, pre- 

 palatine; mx.p, maxillopalatine plate of maxillary; r, 

 vomer; eg, pterygoid; d.px, dentary process of pre- 

 maxillary; mx, maxillary; ip.a, interpalatine ridge; 

 p.as, parasphenoid ; epg, epipterygoid hook. 



commonly called, tarsus. The bones corresponding to our heel bone, calca- 

 neum, and its neighbor, astragalus, unite with the tibia, so that the ankle joint 

 of a bird, like that of reptiles, is between the bones of the ankle, and not as 

 in mammals between the leg and ankle. 



The upper end of the tarsus and its relation to the tendons is a fair index to 

 the position of its owner, being simplest in Ostriches and other birds undeniably 

 low or generalized in character, and more complicated in higher forms, reaching 



