TliK PTEROSAURiA. 



229 



Rre devoid of ribs. The number of vertebra auchylosed 

 together to form the sacrum, is not fewer than three, nor more 

 than six. 



Pjg. 79.— The nearly entire skeleton of Pterodaeiylua apeotabiUs (Von Meyer), as showi 

 by tlie two halves of a split block of lithographic slate, o, the left pre-pubio bone 

 on the right side this bone is not shown, and the ilinm is exposed. 



The tail is very short in Pterodaetylus, and, in this genus, 

 all the vertebrae are movable upon one another ; but in Mham- 

 phorhynchus, it is extremely long, and the vertebrae are 

 immovably fixed by what appear to be ossified ligamentous 

 fibres. 



The vertebral ribs are slender, and the anterior ones, at 

 any rate, have distinct capitula and tubercula. There are 



