24G PALEONTOLOGY 



flyers. The vertebral bodies unite by ball-and-socket joints, 

 the cup being anterior, and in them we have the earliest 

 manifestation of the "proccelian" type of vertebra. The atlas 

 consists of a discoid centrum, and of two slender neurapo- 

 physes ; the centrum of the axis is ten times longer than that 

 of the atlas, with which it ultimately coalesces ; it sends off 

 from its under and back part a pair of processes, above which 

 is the transversely extended convexity articulating with the 

 third cervical vertebra. In each vertebra there is a large 

 pneumatic foramen at the middle of the side. The neural 

 arch is confluent with the centrum. The anterior ribs have a 

 bifurcate head. The dentition is thecodont. 



Genus Dimorphodon, Ow. 



Sp. Dimorpliodon macronyx, Bkd. — The Pterodactyles are 

 distributed into sub-genera, according to well-marked modifi- 

 cations of the jaws and teeth. In the oldest known species, 

 from the lias, the teeth are of two kinds ; a few at the fore 

 part of the jaws are long, large, sharp-pointed, with a full 

 elliptical base ; behind them is a close-set row of short, com- 

 pressed, very small lancet-shaped teeth. In a specimen of 

 Dimorphodon macronyx, from the lower lias of Lyme Eegis, 

 the skull was 8 inches long, and the expanse of wing about 

 ■i feet. There is no evidence of this species having had a 

 long tail. 



Genus Eamphorhynchus, Von Meyer. — In this genus the 

 fore part of each jaw is without teeth, and may have been 

 encased by a horny beak, but behind the edentulous pro- 

 duction there are four or five large and long teeth, fol- 

 lowed by several smaller ones. The tail is long, stiff, and 

 slender. 



The Ramphorhynchus lowjicawhis, R. Gcmminyi, and R. 

 Munstcri belong to this genus. All are from the lithographic 

 (middle oolitic) slates of Bavaria. 



Genus Pterodactyli 8, Ouv. — The jaws are provided with 



