OSTEOLOGY OF BIRDS 



51 



acccssorium is more than usually distinct, and this bone in the recent 

 skeleton is attached after the common rule by ligament merely; it 

 is twisted upon itself, rather long, but not so long in proportion as 

 in Neophron, and supports its ordinary toe, of a joint or phalanx 

 and an osseous claw. 



Perhaps there is no better way of calling the student's attention 

 to the points of interest that are to be found in the feet of these 

 birds than by comparing such a vulture as G y p a r c h u s papa, 

 that has represented in these parts all of the characters of the 

 Cathartidae, with Neophron percnopt e r u s , that as far 

 as we know possesses in its foot all of the characters of the vul- 

 turine birds of the Old World. The joints of the toes follow the 

 usual avian rule of 2. 3, 4 and 5 segments to the first, second, third 

 and fourth toes respectively. In the first or hind toe of Gyparchus, 

 and in all of the Cathartidae, the proximal joint is long and about 

 equally dilated at either extremity, while in Xeophron the end that 

 articulates by its concave trochlear surface with the os nietatarsale 

 accessorium is very much expanded transversely, while at the same 

 time it is compressed from above downward. The bony tubercle 

 found at the under side of the proximal extremity of all of the 

 claws is quite an insignificant affair in our vultures as compared 

 with the protuberance we find in Neophron, and. moreover, the 

 claws are very much more curved in this latter bird than they are 

 in the Cathartidae. The proximal joint of the inside toe of 

 Gyparchus is long, having all the characteristics of the other long 

 segments of the foot, while in Xeophron it is a markedly short and 

 irregular bone, having, to be sure, its ordinary articular surfaces, 

 one at either extremity. This difference can be made more evident 

 by simple measurement: the first and second joints of the inside toe 

 of Gyparchus measure respectively 2.2 and 2.5 centimeters in 

 Xeophron percnopterus, the same segments .7. and 2.4 

 centimeters, respectively. It is very interesting for us to know that 

 in this matter of the shortening of the first joint of the inside toe, 

 Xeophron follows all of the Falconidae or their American repre- 

 sentatives that we have been able to examine. Differences in the 

 hind toe are not striking, the segments in both birds being long and 

 proportionately balanced, but in the outside toe again we discover 

 a leaning on the part of X"eophron towards the Falconidae, while 

 Gyparchus, in common with the rest of its well marked family, still 

 exhibits a proportion in the lengths of the podal phalanges : this 

 time it occurs in the second and third joints of the toe in question. 

 These we will also compare by measurement: in Gyparchus, first, 



