EXTINCT ORDERS OF REPTILES. 229 



are toothed ; but the anterior teeth are large and pointed, 

 and the posterior teeth are small and lancet-shaped. The 

 tail is extremely long and movable. This genus is only 

 known to occur in the Lias. 



3. Rhamphorhynchus, comprising forms in which there are 

 four joints to the wing-finger ; but the front portion of both 

 jaws is edentulous, and may have formed a horny beak, teeth 

 being developed only in the hinder portion of the jaws. The 

 tail is very long. The genus seems to be confined to the 

 Jurassic rocks. 



4. Pteranodon, comprising forms which appear to have 

 the general structure of Pterodadylus, but the jaws are wholly 

 destitute of teeth, and were probably ensheathed in horn. 

 The scapulse and coracoids are anchylosed, and the proximal 

 etds of the scapulse apparently show the unique character of 

 being articulated to the neural spine of one of the dorsal 

 vertebrse. Tlie tail is short and slender. Nydisaurus resembles 

 the preceding in having edentulous jaws, but the scapula 

 is not anchylosed with the coracoid, nor articulated with a 

 vertebra. These two genera comprise gigantic forms of Ptero- 

 sauria from the Cretaceous deposits of North America ; and 

 Prof. Marsh, to whom we owe a knowledge of their charac- 

 ters, regards them as forming a distinct section {Pteranodoiitia) 

 of the order. 



5. Ornithopterus, comprising forms in which the wing- 

 finger has only two phalanges. This genus is only imperfectly 

 known, and may possibly be really referable to the Birds. 



Order IX. Deinosauria {Ornithoscelida, Huxley). — The 

 next order of the Eeptiles is that of the Deinosauria, com- 

 prising a group of very remarkable extinct forms, which are 

 in some respects intermediate in their characters between the 

 Cursorial birds and the typical Eeptiles ; whilst they have 

 been supposed to have affinities to the Pachydermatous Mam- 

 mals. Most of the Deinosauria were of gigantic size, and the 

 order is defined by the following characters : — 



The skin loas sometimes naked, sometimes furnished with a 

 well-developed exoskeleton, consisting of tony shields, mueh re- 

 semhling those of the Crocodiles. A feio of the anterior verte- 

 bra!, were opisthoccelous, the remainder having fiat or slightly 



