THE PTEROSAURIA. 231 



of the Lizard's manus. The terminal phalanx of each of these 

 digits is strong and curved, and was doubtless ensheathed in 

 a horny claw. The fourth, like the corresponding digit in the 

 Crocodile, has four phalanges, the last of which is straight and 

 bears no nail. But these phalanges are enormously elongated 

 and of great relative strength. A strong process projects from 

 the dorsal side of the proximal end of the first phalanx, and 

 doubtless gave attachment to the tendon of a correspondingly 

 powerful extensor muscle. The articular surface below and 

 behind it is concave, and plays over the convex distal pulley 

 of the fourth metacarpal. 



The pelvis is remarkably small. The ilia are elongated 

 bones, produced both anteriorly and posteriorly, as in Birds ; 

 but the rest of the pelvis is not at all ornithic. The flat and 

 broad ischia appear to be united with the pubes into wide 

 bony plates, which pass, at right angles with the ilia, to their 

 median ventral symphysis. A large spatulate bone articulates 

 with each pubis near the symphysis, and seems to be an exag- 

 geration of the pre-pubic process of Lacertilia and Ghelonia. 

 Or it may be (though I do not think this very probable) that 

 the broad flat plates correspond almost altogether to the ischia, 

 and thit the spatulate ossifications are the pubes ; in which 

 case the structure of the pelvis would be a sort of extreme ex- 

 aggeration of that observed in the Grocodilia. 



The hind-limb is small compared with the fore-limb. The 

 fibula is imperfect, and appears to coalesce with the tibia at 

 its distal end. The structure of the tarsus requires further 

 elucidation. In some Pterosauria there seem to be only four 

 digits, with, perhaps, a rudiment of a fifth, in the pes ; but 

 others, such as Jthamphorhynchus Gemmingi, have five digits 

 in the foot. Where there are only four, each digit is termi- 

 nated by a curved and pointed ungual phalanx, and the num- 

 ber of the phalanges from the tibial to the fibular side is 2, 3, 

 4, 5. These digits, therefore, are the hallux, and the three which 

 immediately follow it ; and the rudimentary digit is the 

 fifth. 



The long bones of the Pterosauria have thin walls, enclos- 

 ing a large cavity, which appears to have contained air, as in 

 many birds ; and pneumatic foramina are visible on the sides 

 of the vertebrae. 



The remains of more than twenty species of Pterosauria 

 have been discovered. Some of them are exquisitely preserved 

 in the fine matrix of the lithographic stone of Solenhofen. 



They are thus grouped into genera : 



