CJMOJLIORNIS DIOMEDEUS. 54)7 



ous wall is thin and compact, and the cavity large and 

 smooth, like that of the air-bones in birds of flight. It 

 differs from the femur of any known bird in the pro- 

 portion of its length as compared with its breadth, and 

 from the tibia or metatarsal bone in its trihedral figure 

 and the flatness of the sides, none of which are lon- 

 gitudinally grooved. It resembles most the humerus of 

 the Albatross, both in its form, proportions, and size, 

 but differs therefrom in the more marked angles which 

 bound the three sides. The extremity becomes compressed 

 and expanded, like the distal end of the humerus of the 

 Albatross, but is too much mutilated to allow of the 

 precise degree of similarity or difference to be determined. 

 On the supposition that this fragment of bone is the shaft 

 of the humerus, its length and comparative straightness 

 would prove it to have belonged to one of the longipennate 

 natatorial birds, equalling in size the Albatross. 



The trihedral form of the shaft of the bone resembles 

 that of the upper or proximal half of the ulna of the Al- 

 batross ; but there are no distinct traces of the attachments 

 of the quill-feathers. By the same trihedral form it may 

 be compared with the distal portion of the radius of the Al- 

 batross ; but this idea can only be entertained by supposing 

 the fossil bird to have been of gigantic dimensions, almost 

 realizing the fabulous 'Roc' of Arabian romance; and 

 the other portions of bone associated with it, and most 

 probably parts of the same bird, render this last suppo- 

 sition still less probable. 



The most characteristic of these portions (fig. 230) ap- 

 pears to be the distal end of the tibia, the peculiar troch- 

 lear extremity of which, characteristic of the class of 

 Birds, is sufficiently preserved, although crushed. Their 

 relative size to the preceding bone, on the supposition 



N N 2 



