OF GALLINACEOUS BIRDS AND TINAMOUS. 187 



this fossa is large and cup-like, and, as is always the case when this bone is pneu- 

 matic, the concavity is pierced at its fundus with inlets for the air. In Fowls all this 

 structure is feeble. In the Lapwing, the Loon {Colymbus septentrionalis), and the Cor- 

 morant the fossa is almost obsolete, and no piercings for air are wanted, the cavity 

 of the bone being filled with marrow. In the Toucan {Ramphastos toco) the fossa is 

 large, and so are its basal passages. In the Hawk {Falco cEsalon) the bone is still more 

 scooped ; but in the Owls {Asia otus, Ulula aluco, Strix fiammea) the air-passage is 

 large, but it is not imbedded, it is flush with the inner face of the bone. 



The Hemipodii outdo all other birds, as far as I have seen, in the scooping away of 

 the head of the humerus from within (PI. XXXV. fig. 7). The bone, indeed, seems like 

 a subcylindrical tube which, whilst in a plastic state, had collapsed at one end ; and 

 all the proximal portion of the humerus is a mere shell, the lower edge of this broad 

 part curling inwards like the aperture of a Univalve. 



Two or three pneumatic holes are punched through the floor of this wide fossa. I 

 see nothing to remark upon specially in the forearm-, wrist-, and "hand"-bones 

 (PI. XXXV. fig. 5) of these birds, save that their texture is less coarse than in the Gal- 

 linse. And here it will be well to remark that there is a very notable diflPerence between 

 the Galline and Pluvialine group as to the texture of the skeleton. In the skull espe- 

 cially is this seen ; for its walls in the Fowls and Ostriches are relatively several times 

 as thick as in the Plovers, Tringine birds, and Gulls. In the arboreal birds the skull, 

 and indeed the bones generally, are more delicately cellular, but less thick, than in the 

 great land-birds. In the thin-boned Pluvialinae the bones are, in texture, something 

 between horn and ivory. In the Geese, Swans, and Ducks the skeleton is in many 

 respects like that of the Fowls in its texture, but more elastic and fibrous, and not 

 so thick. 



In the fast-flying Pigeon the humerus is only two-thirds the length of the carpo- 

 metacarpus and phalanges. In the Lapwing (which flies in a dreamy, desultory manner, 

 like a butterfly) the humerus is only slightly shorter than the " hand." In the Swift 

 (Cypselus apus) the humerus measures 6| lines ; the hand 21 fines. This bird, which 

 dashes through the air like the Giant Dragon-fly {JEshna grandis) , we see, has its " hand " 

 three times the length of its " arm." 



In the Quail the humerus is a line longer than the hand ; in the Curassow {Crax 

 globicera) it is three-quarters of an inch longer. 



In Hemipodius varius the humerus (h.) is 1| line shorter than the hand; and in 



Hemipodius ? half a line. So we see that these birds, even in their wings come 



near to both Fowl, Pigeon, and Plover, especially to the last. There are, as usual, two 

 phalanges to the middle digit, proximally, and one distal joint (d.g.) ; also a small joint to 

 the " index." The quill-impressions on the ulna (u.) are scarcely visible, as in Fowls ; 

 and this bone is about thrice the thickness of the radius. The two carpal bones (c.p.) 

 are of the usual size and shape. Lastly, to return to the humerus, the crest for the 



