TIIE FTEHOSAURiA. 



229 



are devoid of ribs. Tlie number of vertebraB anchylosed 

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

 than six. 



PiQ, 79. — The nearly entire sTceleton of Pterodactyliis spectaMUs (Von Mever), as shovri 

 by the two halves of a split block of lithographic slate, a, the left pre-pubic bone 

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



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

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

 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 



