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ERA OF THE NEW RED SANDSTONE. 



TEERESTRIAL ZOOLOGY COMMENCES WITH REPTILES. 

 FIRST TRA.CES OF BIRDS. 



The next volume of the rock series refers to an era dis- 

 tinguished by an event of no less importance than the 

 commencement of land animals. The New Red Sand- 

 stone System is subdivided into groups, some of which are 

 wanting in some places ; they are pretty fully developed 

 in the north of England, in the following ascending 

 order: — i, Lower red sandstone; 2, Magnesian lime- 

 stone; 3, Red and white sandstones and conglomerate; 

 4, Variegated marls. Between the third and fourth 

 there is, in Germany, another group, called the jMuschel- 

 kalk, a word expressing a limestone full of shells. 



The first group, containing the conglomerates already 

 adverted to, seems to have been produced during the time 

 of disturbance which occurred so generally after the 

 carbonigenous era. This new era is distinguished by a 

 paucity of organic remains, as might partly be expected 

 from the appearances of disturbance, and the red tint of 

 the rocks, the latter being communicated by a solution of 

 oxide of iron, a substance unfavourable to animal life. 



The .second group is a limestone ^^ ith an infusion of 

 magnesia. It is developed less generally than some 

 others, but occurs conspicuously in England and 



