SHUFELDT.] OSTEOLOGY OF THE CATHARTIDA. 775 
scribed as the pentosteon* that became anchylosed at this point as the 
bird advanced towards maturity. This is a characteristic feature in 
Neophron also. The trihedral and robust pollex with its undulat- 
ing and superior facet for articulation with its metacarpal, bears below, 
in all of our American Vultures, a freely movable ungual joint; this 
appendage we have already described elsewhere, as well as the circum- 
stances attending its discovery. (Am. Nat., Nov., 1881, p. 906.) In 
the prepared skeleton, freed from all ligaments and soft parts, this 
joint consists simply, and in general terms for all of the Cathartida, 
of a compressed, usually from before, backwards, curved, and pointed 
bone, articulating upon a facette found just below the anterior margin of 
the pollex.t (Plate XV, fig. 105, Gyparchus, and Plate XIX, fig. 110 K, 
Pseudogryphus.) Now this terminal phalanx of pollex may be found 
covered by the common integuments, and not visible when the wing 
has been stripped of its feathers, ¢. g., in Limosa feda and Numenius 
longirostris, or 1t may pierce the skin to be covered by a horny sheath, 
e. g., in many of the Ducks, Geese, and Swans. 
The particular interest which attaches to the jointin the Cathartide is, 
that it passes through the integument, up as far as its base, to be covered 
with a horny sheath outside, and so armed bears a very close resem- 
blance to any of the claws of the feet. This is not the case among many 
other birds, as we have cited above; at least the writer, who has had the - 
pleasure and opportunity to examine a large number of these birds in 
compary with such an astute ornithologist as Mr. Ridgway, failed to find 
it, and we are indeed moreover compelled to acknowledge here that it 
*T have proposed elsewhere the above term for this ossicle when free; I first detected 
it in the carpus of Centrocercus ; itis the fifth segment ofthe avian wrist now recognized. 
It formerly bore the name of the pisiform, which I gave it, and with which it must 
not be confused, nor with a bone so termed by Dr. Coues in his osteology of the 
Laride. (Birds of the N. W., p. 600.) 
+The discovery of this claw excited not a littleinterest at the time. Mr. Forbes, of 
London, kindly noticed it in the following letter to the editors of the American Natu- 
ralist, which contains so much of interest on this particular point, that I take the 
liberty in republishing it. 
[DECEMBER 7, 1881. 
To the Editors of the American Naturalist : 
Gentlemen: I read with much interest Dr. Shufeldt’s article in your journal for 
November last, on the claw on the “index”! of the Cathartide, to the existence of 
which he had previously called my attention when I had the pleasure of making his 
acquaintance in Washington last month. Dr. Shufeldt certainly deserves great credit 
for being the first to detect a structure, which has previously, so far as I am aware, 
escaped the notice of all observers. I may add that since my return I have been able 
to confirm the truth of Dr. Shufeldt’s statements on specimens of Catharies aura and 
C. atrata in my possession. 
Allow me, as one perhaps more favorably situated than Dr. Shufeldt has been as 
regards the literature of ornithology, to call my friend’s attention to Nitzsch’s ‘‘ Osteo- 
graphische Beitrige zur Naturgeschichte der Vogel,” published at Leipzig in 1881. In 
that? he will find an excellent account of the claw and phalanx in question as it exists 
in many other birds. 
Nitzsch does not seem to have observed it in the Cathartida, but found itin Haliatius 
albicilla, Tinnunculus alaudarius, and some others of the Falconide. It is very conspicu- 
ous in Pandion. In fact the occurrence of such a claw is of very frequent occurrence 
in the class Aves, though by no means universal amongst them. Amongst birds in 
which it may be well seen, I may mention Struthio and Rhea, Cypselus, Caprimulgus, 
the Rallide and Parride. Such a claw must not be confounded, as has been done by 
_some writers, with the long ‘‘spurs” covered by epidermic tissues, formed by outgrowths 
from the metacarpal elements, of most birds, as Parra, Palamedea, Plectropterus, &c. In 
fact, the two may, as in Parra or Plectropterus, co-exist. Believe me, yours very truly, 
V FORBES, 
Prosector to the Zoological Society of London. ] 
(Am. Nat., Feb’y, 1882, p. 141.) 
1The digit of the Avian manus, called ‘‘index’’ by Professor Owen, is now universally recognized by 
anatomists as really the pollex. 
2Ueber das Nagelglich der Fligelfinger, besonders der Daumen,” pp. 89-97. 
