31G 
MR W. T. PYCRAFT OX THE BIRD’S WING 
In the skeleton of these wings we should find more differences. 
Thus, in the Bat (Fig. 2, B), all five digits are represented. The 
pollex, or thumb (D), is often long and armed with a large claw. 
The remaining digits are of great length and slenderness, and so 
arranged that they support this membrane much as the ribs of an 
umbrella support the covering. 
In the Pterodactyle (Fig. 2, A) four or five digits are 
recognizable ; but of these, only the last, or little finger, takes 
part in supporting the wing-membrane, and on this account it 
is prodigiously developed. The remaining fingers are small and 
weak, and would probably have disappeared in course of time had 
not the species itself become extinct. 
In the bird (Fig. 3), as we have just pointed out, only three 
digits remain, and these represent the thumb, and first and 
second fingers. This wing is seen in its most primitive form in 
Archaeopteryx, the extinct bird of the Solenhofen Slates of 
Bavaria. In the manus of this bird, although no more than 
three fingers are present, the wing is yet more primitive in type 
in that each digit bears a large, ungual phalanx, which supported, 
during life, a still larger sheath constituting the claw. Only in 
the young Ostrich among living birds has a claw been found 
on the third digit. That of the first and second is often present, 
and even large, e.g .,— the South American Opisthocomus, or 
Iloatzin. 
The metacarpal bones of the Bat and the Pterodactyle are free. 
In the bird the three metacarpals are fused together: the first is 
very small, the second and third subequal. 1'he fingers are 
peculiar in that the first, or thumb, is short ; the second, or index, 
is relatively long, whilst the third is again short (Fig. 3 and Fig. 1). 
The number of phalanges in each digit varies. Thus the thumb 
may have one or two phalanges, the second finger three, and third 
two. In Archaeopteryx the third digit had four phalanges. As 
will be seen in Fig. 3, the hand and fore-arm, when extended, 
form a long, bony rod, which serves for the support of the bases 
of the quill-feathers. These, as we have already seen, almost 
entirely take the place of the anterior and posterior patagial 
membranes of the Bat and Pterodactyle. 
As we have already pointed out, the difference between the 
