12 INTRODUCTION. 



of this formation, was co-existent with their primeval exis- 

 tence. This author very justly observes, that "whatever 

 the kind of animal may have been which first appeared on 

 the surface of our planet, we may be certain that it was 

 consistent with the wisdom and design which have always 

 prevailed throughout nature, and that each creature was 

 peculiarly adapted to that situation destined to be occupied 

 by it." 



The Grauwacke group,* which lies above the last men- 

 tioned formation, contains many genera of shells and other 

 organic remains. Some of these genera, which consisted 

 of innumerable species, are, in the superior deposits, totally 

 wanting, being entirely extinct, to the best of our know- 

 ledge ; while other genera, unknown in the vast deposits of 

 the inferior formations, are here found in great abundance 

 and in numerous species. 



In the strata superior to this, the Carboniferous group, 

 we find, for the first time, a deposit of fresh water forma- 

 tion, and the fossil remains of the group are increased by 

 the addition of plants and fishes. 



Superior to this again we find the New Red Sandstone 

 group, and in it some of the reptilia, the great Saurian 

 animals. 



Higher up, the Oolitic group presents us with a much 

 greater vaiiety of reptilia, and for the first time we have 

 the indication of Mammalia in the Didelphis Bucklandi. 

 Plants, zoophytes, shells, Crustacea, &c. are numerous, 

 and insects have also been observed in it.f 



(Agalysian rocks of Brogniart) presenting nearly the same character in 

 all parts of the world, seem, by their attrition, to have formed, in subse- 

 quent deposits, the whole mass of superincumbent rocks, except those of 

 volcanic origin. 



* Hemilysiens of Brogniart includes this and the subsequent group. 



t In the U. States, no indication of the Oolitic group has been observed. 

 In England it is a very important formation, consisting of numerous sub- 

 formations, of which the Lias is the lowest. 



