18 GEOLOGY. 



latitudes about equally removed from the equator with our 

 own, of the same fossil animals, disproves the once favourite 

 theory of their extinction by a reduction of temperature, oc- 

 casioned by a change of the poles of the earth. Bones of the 

 following mammalia have been procured from the deposits 

 above named. Megatherium Cuvieri, Megalonyx, Mastodon 

 giganteum, Elephas primigenius, a Bos, an Equus, a Cervus, 

 and the right ramus of the lower jaw of a new genus, the 

 Harlanus Americanus of Owen (Sus Americanus of Harlan). 

 In the post-pliocene sand formation which underlies the fossil 

 mammals, most of the species of shells now existing in the 

 neighbouring sea have been found ; and in the same formation, 

 but nearer the surface, ribs and vertebrae of a whale, and the 

 right os-femoris of an extinct Chelonia (Chelonia Couperii of 

 Harlan). 



It is believed, that the Miocene formation has not yet been 

 discovered cropping out at the surface in Georgia, but as the 

 writer of this article found two specimens of the Fusus quad- 

 ricostatus on the beach of Long Island near St. Simon's Island, 

 after the gale of the 12th of October, 1846, there is no doubt 

 that it approaches very near to the surface. 



No fossils have been found between the post-pliocene de- 

 posits already mentioned, and the Burr-stone formation of the 

 Eocene ; and this part of the State presents no object of in- 

 terest to the geologist, except the existence of two nearly pa- 

 rallel terraces, terminated to the east by well defined escarp- 

 ments. 



From the ocean, the land ascends by a gradual slope, to 

 the height of from ten to twenty feet, when, at a distance of 

 from twenty to thirty miles, it rises by an abrupt step to the 

 elevation of seventy feet above tide water: at which elevation 

 it runs back about twenty miles, when another and similar 

 step of about the same height occurs These escarpments 

 have obviously been sea-cliffs or margins ; and the manner of 

 their formation has been very satisfactorily explained by Dar- 

 win in his Journal of Researches, &c., where he notices a 

 series of similar cliffs in Patagonia. He supposes, in the first 

 place, a period of slow and gradual elevation of the land, 

 converting that portion of the sea lying between the western 



