52 



FOSSIL REPTILIA OF THE 



phalanx 3) is 5 inches 6 lines in length ; near its distal end is part of the slender terminal 

 phalanx of this digit (/r, 4)- 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 {ir,,,,; PI. 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 Q jj) 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 

 fibula is hidden from view. The trochlear termination of the distal end of the tibia is 

 better marked than in Crocodilus, or even than in Scelidosaiirus (' Monograph on Oohtic 

 Reptilia,' Part 11 (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 Dimorpliodon 



1 'Ossemens Fossiles,' 4to, v, pt. ii, p. 371. 



~ Beitrage zur Kentniss verscbiedener Reptilien der Vorwelt, in 'Nova Acta Acad. Natur. Curios.,' 

 Leopold Carol., &c., ^ito, torn. xv. " lleptilien aus dem lithographischen Schiefer, Pterodactylus crassiros- 

 tris, nobis, tabs. VII — X." 



3 'Bridgewater Treatise,' Svo, 1836, pi. 22. 



4 Owen's 'Palaeontology,' 8vo, 1861, fig. 97. 



