THECODONTIA. 275 



chalk of Kent, attained dimensions very little inferior to those 

 of the greensand Pterodactyles. 



With regard to the range of this remarkable order of flying- 

 reptiles in geological time, the oldest well-known Pterodactyle 

 is the Dimorphodon macronyx, of the lower lias ; but bones of 

 Pterodactyle have been discovered in the coeval lias of Wir- 

 temberg. The next in point of age is the Dimorphodon Ban- 

 thensis, from the " Posidonomyen-schiefer " of Banz in Bavaria, 

 answering to the alnm shale of the Whitby lias ; then follows 

 the P. Bucklandi from the Stonesfield oolite. Above this 

 come the first-defined and numerous species of Pterodactyle 

 from the lithographic slates of the middle oolitic system in 

 Germany, and from Cirin on the Ehone. The Pterodactyles 

 of the Wealden are as yet known to us by only a few bones 

 and bone fragments. The largest known species are those 

 from the upper greensand of Cambridgeshire. Finally, the 

 Pterodactyles of the middle chalk of Kent, almost as remark- 

 able for their great size, constitute the last forms of flying 

 reptile known in the history of the crust of this earth. 



Order VII. — Thecodonts. 



Char. — Vertebral bodies biconcave : ribs of the trunk long 

 and bent, the anterior ones with a bifurcate head : 

 sacrum of three vertebras : limbs ambulatory, femur 

 with a third trochanter. Teeth with the crown more or 

 less compressed, pointed, with trenchant and finely 

 serrate margins : implanted in distinct sockets. 



Genus Thecopontosaurus. R. and S. 



Sp. Thecodontosaurus antiquus. — In 1836 certain reptilian 

 remains from the " dolomitic conglomerate" at Redland, near 

 Bristol, were described by Messrs. Riley and Stutchbury. 



* Geological Transactions, 2d series, vol. v., p. 344. 



