148 
Mr. P. L. Sclater on the Claws 
Common Fowl and of many others of the Phasianidse. It 
consists of a bony core covered with a thick horny coat, and 
may, as I shall presently show, arise either from the carpus 
or from the metacarpus. Its function appears to be purely 
that of a weapon of offence. It is found in many quite 
unconnected groups of birds, such as the Spur-winged 
Plovers (Hoplopterus) , the Jacanas (Parra), the Screamers 
(Chauna and Palamedea), the Spur-winged Geese ( Plectro - 
pterus) , and the Torrent-Ducks (Merganetta). These genera 
are widely separated ; and it is obvious that in each case the 
spur must have been specially developed. 
On the other hand, the claws on the wings of the bird, as 
Mr. Jeffries has likewise clearly explained, are the homologues 
of the claws on the feet : that is, they are dwarfed represen¬ 
tatives of the nails on the anterior extremities which birds 
have inherited from their reptilian ancestors. They are 
absolutely useless to birds in their present state of existence 
—at any rate when the bird is adult—as they are so covered 
over by the feathers that it is in most cases very difficult to 
find them. If, however, a careful search be made at the end 
of the first and second digits of certain birds, a small claw 
will be discovered investing the last phalanx. Usually, if 
present, the claw is found at the end of the first digit; more 
rarely it occurs on the second. When it is placed on the 
first digit it will be found at the end of the second (or 
ungual) phalanx; when it occurs on the second digit it will 
be found at the end of the third (or ungual) phalanx. This 
shows that the claw is a remnant of the nail that formerly 
terminated the first two digits, and proves that, as Mr. Jeffries 
says, the ancestors of birds had a two-jointed first finger and 
a three-jointed second finger, both provided with claws. 
This was also the case with Archaeopteryx , which had, more¬ 
over, a claw on its third digit *. But such is not the case 
in modern birds, in which the claws, when still existing, are 
found only at the extremities of the first and second digits. 
* My attention having been called to this subject, I have had 
See Vogt’s description and figure of the manus of Archceopteryx, 
Ibis, 1880, pp. 438, 443. 
