O. C. Marsh—The Wings of Pterodactyles. 255 
the outer or ulnar side, but American specimens prove conclu- 
sively that they belong on the radial side. 
The nature of the so-called pteroid bone has been much 
discussed, but without a satisfactory conclusion. fter a care- 
ful study of many specimens, the writer is disposed to regard 
it, not as an ossified tendon, but as a part of the first digit, or 
thumb, which is usually considered wanting in Pterodactyles. 
According to this view, the “Jateral carpal” would probably 
e the metacarpal of the same digit. In favor of this interpre- 
_ tation, it may be said— 
(1.) That the position and structure of this appendage of the 
carpus correspond closely with that of the first digit in some 
other reptiles, for example, /guanodon. 
(2.) The “lateral carpal” unites both with the distal carpal 
and with the “ pteroid” by very free, well-defined articulations. 
(3.) In American specimens, the “lateral carpal” stands 
nearly at right angles to the wrist, and the “pteroid” is much 
bent near its articular end. 
(4) In no Pterodactyle known is there any remnant of a 
digit outside the wing finger, where the membrane might be 
expected to retain it. 
).) This view would make the wing finger the fifth digit, the 
same to which the membrane is attached in the hind foot. 
and they vary much in other reptiles which have the digits 
highly specialized. This subject will be more fully discussed 
by the writer elsewhere. 
According to the above interpretation, there are five digits in 
the hand of Pterodactyles, although not the five often given in 
restorations. The first digit, the elements of which have been 
considered, undoubtedly supported a membrane in front of the 
arm. The second, third, and fourth are small, and armed with 
claws. The large wing finger is the fifth, corresponding to the 
little finger of the human hand. 
he metacarpal bones are much elongated in the Pterodac- 
tyles with short tails, and quite short in those, like the present 
Specimen, that have the tail long. The metacarpal of the wing 
finger is always large, and robust, while those of the claw-bear- 
Ing digits are usually quite slender. In Pleranodon, the second 
metacarpal is a slender thread of bone, throughout most of the 
length, while the third and fourth are attenuated splint bones, 
Incomplete above. = 
_ The phalanges of the three middle digits are quite short, and 
the terminal ones supported sharp claws. The wing finger has 
four greatly elongated phalanges, the last being a styloid bone, 
