168 THE RECENT. 



tiary epoch advances, the boreal races retreat farther to the 

 north, some of the old pliocene families again return and 

 spread over European latitudes, and other and newer forms, 

 in the course of creation, begin to appear. 



It is now the current era of geological history, whose 

 vital record is the silts and marls of filled-up lakes, the 

 alluvium of rivers and estuaries, the growth of peat-bogs 

 and morasses, the stalagmite of fissures and caverns, and 

 the tufa and ashes of volcanoes. In these superficial ac- 

 cumulations, which meet us at every turn, and are still in 

 course of formation, every imbedded organism is fresh and 

 familiar. With the exception of a few extinctions, the 

 species yet nourish in the same latitudes, and the lists of 

 the palaeontologist become identical with those of the 

 botanist and zoologist. The peat-bogs of Europe are re- 

 plete with the mosses, grasses, willows, hazels, birches, firs, 

 and oaks that still spread over our swamps, and adorn our 

 forests. The tundras of Siberia, the jungle-soil of India, 

 and the cypress-swamps of America, are in like manner 

 composed of the plants now peculiar to these regions; and 

 though in the course of geological change, local features 

 may have varied, the main aspects of the Current Flora 

 continue, zone for zone, and province for province, with 

 little alteration or disturbance. 



When we turn to the Fauna, the case is much the same. 

 The most ancient lake-marls of Europe are thronged with 

 lymnea, paludina, cyclas, planor'bis, scarcely, if at all, dis- 

 tinguishable from those that now people our fresh- water 

 ponds ; and the marine shells of our estuarine silts and 

 raised beaches the mussels, cockles, oysters, periwinkles, 

 whelks, silver-shells, and clams with a few local variations, 

 are identical with those that inhabit the surrounding seas. 

 When we turn to the terrestrial fauna, the change, chiefly 



