LIASSIC FORMATIONS. 



77 



in resting or moving on dry ground was that indicated in the restoration of the skeleton 

 in PI. IV. 



The hind limbs of DimorjjJiodori are, nevertheless, larger and stronger in proportion 

 than in other Pterosauria. The femur, in most species, equals the humerus in length, and, 

 in Dimorphodon, also in thickness. In Pterodactylus longirostris and Pt. Koc1iii*C(\s, femur 

 is the more slender bone ; in Rampliorliynchus it is likewise shorter than the humerus. 



The tibia, more slender than the antibrachial bones, in Pterodacti/lus longirostris and 

 Pt. Kochii, is of equal length therewith. In Bimorphodon the tibia is less slender in pro- 

 portion to the antibrachium, and is longer by one seventh. In Pamphorhynchus it is 

 much more slender than the antibrachium, and is nearly one third shorter. The ankle- 

 joint works between the tibia and tarsus, which, as in other Reptiles and Mammals, is 

 distinct from the metatarsus. There is no calcaneal prominence, and the foot admits of 

 easy rotation, as in the ' Restoration,' PI. XX, fig. 2, where the inner toe is turned out- 

 ward and the sole presented to view, to show the application of the wing-toe in flight to 

 the interfenioral web. 



Whether the trochlear terminal joint of the tibia be ossified from a separate centre in 

 the Pterodactyle as in the Bird requires a specimen of the requisite immaturity for deter- 

 mining. If the hind limbs and pelvis presented the structure for sustaining and moving 

 the animal erect on land, an epiphysial state of the articular ends of the long bones might 

 be physiologically inferred. I conclude, from the absence of the modifications essential to 

 bipedal station and progression in Pterosauria, that the articular ends of both femur and 

 tibia, including the distal condyles of the latter bone, were co-ossified with the shaft as in 

 other Saurians. 



AVhen in warm-blooded Vertebrates,whether Birds or Mammals, the metapodial elements 

 of different toes coalesce, the epiphyses of such coalesced series, or 

 • cannon bone,' are usually connate, forming a single bone. As, e.g., at 

 the proximal end of the Cow's and Bird's metatarsus (figs. 3 and 4, c)} 

 and also even at the distal end of the cannon-bone in Ruminants 

 (fig. 3, d). I demonstrated the fact in both the metacarpus and meta- 

 tarsus of a young Giraffe, in my ' Hunterian Lectures' of 1851. The 

 specimens are Nos. 3631 and 3635 in the Osteological Collection of 

 the Royal College of Surgeons (' Catal.' 4to, 1853, p. 601). 



The distal trochlear end of the Bird's tibia, in its epiphysial state 

 (fig, 4, d), answers to the distal trochlear epiphysis of the Ruminant's 

 tibia (fig. 3, a). In its anchylosed state the distal bicondylar troch- 

 lear joint or end of the Bird's tibia answers to the distal bicondylar j^^j^j^^^j B^rd. 

 trochlear joint or end of the Pterosaur's tibia. The proximal 



1 " The upper articular surface is formed by a single broad piece. The original separation of the 

 metatarsal bone below into three pieces is plainly indicated."—" On the Anatomy of the Southern Apteryx,"! 

 •Trans. Zool. Soc.,' ii (1838), p. 293. 



