OF GALLINACEOUS BIRDS AND TINAMOUS. 223 



angular process is a small air-hole. The posterior or external angular process (fig. 7) 

 is a very small tubercle : this is all there is to represent the long horn curling upwards 

 here in the " Gallinai " (PI. XXXVI. fig. 9), an inch in length in the Cock of the "Woods. 

 Altogether the mandibles are struthious, and the articular end of the jaw, with its 

 deeply scooped, obliquely oval posterior face, is as much like that of the Rhea 

 (PI. XLII. figs. 4, .5, 6) as can be, and as perfectly diagnostic of the afiinities of the 

 bird. 



I have no os hyoides to work from, and thus, unfortunately, lose an important part 

 of my demonstration. The viscera also must be left for some future paper. 



In what follows I hope to be able to show that the remoter parts of an organism are 

 less to be depended upon for the demonstration of special affinities than the central, 

 and that any very slight hint given by the head may be acted upon to a very unex- 

 pected extent by the hands and feet. Still there is " no schism in the body," however 

 great the amount of " adaptive modification " to which it has been subjected ; and the 

 " kingly crowned head " is always in beautiful harmony with 



" Our steed the leg, the tongue our trumpeter. 

 With other muniments and petty helps 

 In this our fabric." 



I have to keep to the parts that immediately surround the pituitary space for the 

 organic centre of the skull, and, in a certain sense, of the whole skeleton — the spine 

 being viewed as a sort of extended and secondary point, or rather series of points, of 

 departure. 



We shall always find the outlying parts the most modified, even in the head ; in the 

 body, not only " the muniments and petty helps," but even " our steed the leg " is ready 

 to undergo very sudden changes as we pass from species to species. 



The whole skeleton of the Tinamou (PI. XXXIX.) is very light and spongy, and is 

 pretty accurately intermediate in this respect between the Guatemalan Tree-Partridge 

 {Dendrortyx) and the Curassow {Crax). "With the exception of the caudal vertebrae, 

 the furcula, the wing-bones from the elbow, and all the leg-bones, the skeleton is 

 delicately pneumatic and spongy ; the bones that contain marrow, however, are not 

 much heavier in build than those of the Dendrortyx, and very much more typical in 

 this respect than those of the Fowl. That seems something sudden ; yet any one well 

 acquainted with the structure of the bones of the great " Struthionidse " will remember 

 what exquisitely light diploe they possess. It is the Apteryx that stands so low down 

 in this matter, the Brush-Turkey {Talegalla) being a step or two above it. 



There are twenty-two vertebrae between the skull and the sacrum : the last of these 

 is free ; in front of that there are four which are coalesced into one piece {d.). The first 

 of these has a large floating rib {cr.), and the rib of the last, or separate dorsal, has a 

 half-sized floating hsemapophysis ; so that only three of the dorsals have perfect sternal 

 ribs {dr.). The penultimate cervical has a large floating rib, an inch long ; the antepenult 



VOL. V. PART III. 2 G 



