52 
FOSSIL REPTILIA OF THE 
phalanx 0,^ 3) is 5 inches 6 lines in length ; near its distal end is part of the slender terminal 
phalanx of this digit There is no trace of a fourth unguiculate digit, and I return to 
Cuvier’s view of the structure and homologies of the hand of the Petrodactyle,^ which I 
had abandoned in favour of the seemingly more perfect evidence supporting Professor 
Goldfuss’ restoration of Pterodactylus crassirostris,^ adopted by Buckland ® and myself.^ 
The metacarpal of the left wing-finger m', FI- XVIII) lies beneath the back part of 
the skull, and is over-lapped by the superorbital part of the frontal. Portions of two of 
the unguiculate digits of the same fore-paw G n) are seen in the wide narial vacuity. 
The definition and finish, so to speak, of the joints of the wing-finger are worthy of 
note, especially of that between the metacarpal bone and proximal phalanx. In Reptiles 
generally the articular extremities of the long bones are not very definitely sculptured, and 
do not manifest that reciprocal adaptation of their inequalities which are observed in the 
joints of Mammals and Birds. The difficulty of determining the coadapted extremities of 
detached bones of Reptiles is increased by the great thickness of the cartilage which covers 
them and renders their mutual contact more intimate, and which is always wanting in 
fossil bones. The Pterosaurian modification is, however, purely adaptive ; and the relation 
to Warm-blooded Vertebrates in this respect is one of analogy. An argument in favour 
of avian affinity from the joint-structures could only be propounded by one not gifted with 
the judgment needed to deal with problems of this nature. 
The left femur (65') preserves its natural articulation with the acetabulum ; the head is 
bent forward from the line of the shaft for an extent like that at which the condyles are 
produced backward ; the shaft is straight, the great trochanter is feebly developed. There 
is no evidence of a modification of the distal condyle for the interlocking articulation with 
the fibula, which in Birds relates to their bipedal station and walk. The length of this 
femur is 3 inches 4 lines 
The left tibia (66'), bent back at an acute angle upon the femur, measures 4 inches 10 
lines in length. There is no trace of patella, nor has this sesamoid bone been found in 
any Pterosaur. The inner side of the bone being exposed, the styliform rudiment of the 
fibnla is hidden from view. The trochlear termination of the distal end of the tibia is 
better marked than in Crocodilus, or even than in Scelidosaurus (‘ Monograph on Oolitic 
Reptilia,’ Part II (1863), p. 16, PI. X, 66), and consequently approaches more nearly to 
the characteristic form of the joint in Birds, The resemblance to the bicondyloid termina- 
tion of the femur is instructively shown in the distal portion of the Pterosaurian tibia 
figured in PI. XIX, figs. 8 and 9, and in the distal half of the right tibia of Bimorphodon 
1 ‘Ossemens Fossiles,’ 4to, v, pt. ii, p. 371. 
2 Beitrage zur Kentniss verschiedener Reptilien der Vorwelt, in ‘Nova Acta Acad. Natur. Curios.,’ 
Leopold Carol., &c., 4 to, tom. xv. “Reptilien aus dem lithographischen Schiefer, Pterodactylus crassiros- 
iris, nobis, tabs. VII — X.” 
* ‘Bridgewater Treatise,’ 8vo, 1836, pi. 22. 
^ Owen’s ‘Palaeontology,’ 8vo, 1861, fig. 97. 
