cm 



/ S r-i-il^Lg / 



COLLECTIONS! P^ I fossil 



FBOM MINERALS DOSSIL MAMMALS V F055I L MAMMALS ttE p T | LES 



J I | (mI 5 TO DON 6) | ^°"" CAMELi ET ^( g Sfoi A »" S> 



Vj vjl. Elevators O 



2. Fossil Fishes 



FOURTH FLOOR 



Foreword ox Fossil Vertebrates 



In the East Corridor, and the South Par il ion at the left, as well as in 

 the East Wing and Southeast Pavilion at the right are displayed the fossil 

 mammals, reptiles and fishes. 



In a general way, fossils are the petrified remains of plants or animals 

 that lived at some past period of the earth's history. In many instances we 

 have not the objects themselves but only their casts or impressions in the 

 rocks. This is particularly the case with shells. Sometimes, as with the 

 bones of the great Irish elk the objects have been buried in swamps or bogs, 

 and in a few rare instances as with the mammoth and woolly rhinoceros, 

 entire animals have been preserved for thousands of years in ice or frozen 

 mud. Fossils are found in localities where the dead animals or plants 

 have gradually been buried under layers of sediment to such a depth that 

 they come in contact with the mineral waters of the earth and finally be- 

 come petrified. Later through subsequent upheaval and erosion they are 

 again brought to or near the surface of the earth. Petrifaction is the slow 

 replacement of animal or vegetable material by such minerals as carbonate 

 of lime or silicate. The process is very slow and for this reason flesh is 

 never petrified. Fossil beds are found in every continent. In our own 

 country, Texas, Montana, Wyoming, and the Bad Lands of South Dakota 

 are famous for their large fossil beds, and many of the finest and rarest 

 fossils in the Museum were obtained in these localities. 



As it takes thousands of years for the various layers of earth to accumu- 

 late over the bones, and for the latter to become petrified, the study of 

 fossils and the strata in which they are found is an important aid in de- 

 termining the age of the earth and the succession of life thereon. Nearly 



