PAL^OZOOLOGY : FOSSIL ANIMALS. 267 



horizon by which the geologist may recognise his position, 

 and obtain safe conclusions in regard to the identity or 

 relative antiquity of formations, the periodical repetition of 

 certain strata, their parallelism, or their entire suppres- 

 sion. If we would thus comprehend in its greatest simpli- 

 city the general type of the sedimentary formations, we find 

 in proceeding successively from below upwards : 



1. The transition group, divided into lower and upper 

 greywacke : this group includes the silurian and devonian 

 systems ; the latter formerly called the old red sandstone. 



2. The lower trias ( 313 ), comprising the mountain lime- 

 stone, the coal measures, the lower new red sandstone 

 (todtliegendes), and the magnesian limestone (zechstein). 



3. The upper trias, comprising the hunter or variegated 

 sandstone, ( 314 ) the muschelkalk, and the keuper sandstone, 



4. The oolitic at Jurassic series ; including the lias. 



5. The cretaceous series, the quadersandstein, the lower 

 and the upper chalk. This group includes the Floetz forma- 

 tions of Werner. 



6. The tertiary group, as represented in its three stages 

 by the calcaire grossier and other beds of the Paris basin, 

 the lignites or brown coal of Germany, and the sub-apennine 

 group in Italy. 



To these succeed transported soils (alluvium), containing 

 the gigantic bones of ancient mammalia, such as the 

 Mastodons, the Dinotherium, and the Megatheroid ani- 

 mals, among which is the Mylodon of Owen, an animal 

 upwards of eleven feet in length, allied to the sloth. As- 

 sociated with these extinct species are found the fossil 

 remains of animals still living: elephants, rhinoceroses, 

 oxen, torses, and deer. Near Bogota, at an elevation of 

 8200 French feet above the level of the sea, there is 



