270 THE ANATOMY OF TEETEBEATED ANIMALS. 



but the rest of tlie 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 spatnlate bone 

 articulates with each pubis near the symphysis, and seems 

 to be an exaggeration of the pre-pubic process of Lacertilia 

 and Chelonia. Or it may be (though I do not think this 

 very probable) that the broad flat plates correspond almost 

 altogether to the ischia, and that the spatulate ossifications 

 are the pubes; in which case the sti-ucture of the pelvis 

 would be a sort of extreme exaggeration of that observed in 

 the Crocodilia. 



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 fur- 

 ther 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 Wiamphorhynchus Getnminfji, have five 

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

 terminated by a curved and pointed ungual phalanx, and 

 the number 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, in- 

 closing 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 exquisitelypreserved 

 in the fine matrix of the lithographic stone of Salenhofen. 



They are thus grouped into genera : — 



A. With two joints in the ulnar digit of the manus. 



Ornithoptertis. 



B. With four joints in the ulnar digit. 



a. The jaws strong, pointed, and toothed to their anterior 

 extremities. The tail very short. The metacorpiis 

 usually longer than half the length of the antebrachiuin. 

 Pterodacti/lus. 



