\68 SKETCHES OF CREATIOX. 



with scales or bony plates, and almost always possess four 

 extremities; their eyelids are movable, and their two jaws 

 move vertically like those of higher animals. The serpents 

 are equally clothed with scales, but their bodies are more 

 elongated, and destitute of limbs; their eyelids are immov* 

 able, and each of their jaws is in two pieces ; and they have, 

 besides, an extra pair of jaw-pieces in the roof of the mouth. 

 The extinct orders are Pterodactyls, or flying reptiles 

 Enaliosaurs, or marine reptiles, and Labyrinthodonts, 01 

 reptiles with very complicated structure in the substance 

 of their teeth, and, sometimes at least, with frog-like forms. 

 They possess affinities both with true reptiles and with 

 batrachians. 



In 1828, Dr. Duncan, a Scotchman, had his attention ar 

 rested by what appeared to be tracks of a reptile imprinted 

 upon the surface of solid sandstone at Dumfriesshire. A 

 few years later, tracks somewhat resembling the impression 

 of a human hand were observed upon similar sandstone in 

 Saxony. These were also attributed to reptiles. In this 

 country, Dr. Deane and Professor Hitchcock noticed upon 

 red sandstones, in the valley of the Connecticut River, nu- 

 merous tracks w T h;ch they were inclined to attribute to 

 birds, as they were evidently made b.y three-toed bipeds. In 

 1836, Professor Hitchcock published the first systematic 

 account of these footprints, in which he pronounced them 

 to be mainly the tracks of birds — Ornithichnites — a con- 

 clusion which is very questionable. In 1844, Dr. King, 

 of Philadelphia, also described several kinds of footprints 

 upon rocks then supposed to be carboniferous, but since 

 shown to be of the same age as the sandstones upon which 

 all the other known tracks had been observed. The rocks 

 are the "New Red Sandstone," belonging to the lower part 

 of the Jurassic system, or the upper part of the Triassic. 

 The position is a considerable distance above the coal. 



