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 {Ho])lopterus) , the Jacanas {Parr a), the Screamers 

 {Chauna and Palameded), the Spur-winged Geese {Plectro- 

 pterus) , and the Torrent-Ducks {Merf/anetta). 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 Archceupteryx, 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 aud figure of the man us of Archceopteryx, 

 Ibis, 1880, pp. 438, 443. 



