The Ulna of a bird

The ulna, which often presents a series of tubercles, indicating the attachment of the secondary quill-feathers, is usually a stronger, and a longer, bone than the radius. There are only two carpal bones, one radial and one ulnar.

In the Apterygidae and in the Casuaridae, there is but one complete digit in the manus. It appears to answer to the second of the pentadactyle limb, and is provided with a claw. In the Struthionidae and Rheidae, and in all Carinatae, there are three digits in the manus, which answer to the pollex and the second and third digits of the pentadactyle fore-limb; and the metacarpal bones of these digits are anchylosed together. As a rule, the metacarpal of the pollex is much shorter than the other two; that of the second digit is strong and straight, that of the third is more slender and bowed, so as to leave an interspace between itself and the second, which is often filled up by bony matter. The pollex has two phalanges, and the second of them is, in many birds, pointed, curved, and enensheathed in a horny claw. The second digit has three phalanges, and the terminal phalanx is similarly provided with a claw in sundry birds. In the ostrich, both the pollex and the second digit are unguiculate. The third digit never possesses more than one or two phalanges, and is always devoid of a claw.

It is a singular circumstance that the relative proportions of the humerus and the manus should present the most marked contrast in two groups of birds, which are alike remarkable for their powers of flight. These are the Swifts and Humming-birds, in which the humerus is short and the manus long; and the Albatrosses, in which the humerus is long and the manus relatively short.

In the Penguins, the pollex has no free phalanges, and its metacarpal bone seems to be anchylosed with that of the second digit. The third metacarpal is slender and straight. The bones of the manus are singularly elongated and flattened: