118 FOSSIL AQUARIUM 



In the fourth alcove are shown the ganoid fishes wliich dominated the 



waters during the Age of Reptiles. They were of many 



kinds and sizes, most of them with lozenge-shaped scales 



of l)one, with enamelled surface. One of the few survivors "Ainia" of this 



ancient group is here show-n living ''in a window aquarium", to give the 



visitor a clearer idea of the fishes of the "IMiddle Ages" of the world. 



In the fifth alcove are the petrified fishes of the Age of Mammals. By 

 _ . this time nearly all of the primitive fishes, like sharks, lung- 



fishes and ganoids, had become extinct; and the common 

 forms were bony-fishes, or teleosts, closely related to our herrings, 

 perches, mackerels and daces. 



[Return to the South Pavilion or Hall of Mastodons and Mammoths.] 



SOUTH CENTRAL WING 



Geology and Invertebrate Paleontology 



Turning northward at the center of the Quaternary Hall containing 

 the mastodons and mammoths, the visitor enters the Sottth Central Wing 

 of the building and is in the Hall of Geology and Invertebrate Paleon- 

 tology. PaUeontology is the science of the ancient life of the earth; its 

 field is the study of the fossilized shells and other hard parts and the 

 various kinds of imi)rints left ])y the animals formerly inhabiting the 

 seas and lands, and preservetl in dejiosits which i\ow form our stratified 

 rocks. As normally the uppi>r layers of a series of strata are more recent 

 than the lower, the fossils reveal the succession of life forms in the earth's 

 crust and thus are of the highest value and interest to the student of 

 historical geology. Since, however, the remains of only a small propor- 

 tion of the animals living at a given jieriod are i)ermanently preserved 

 in the marine, river, lake and subaerial dei)()sits of that period, the 

 geological record of animal and plant forms is far from com])lete. Inas- 

 much as invertebrate animals are far less free in their movenu^nts than 

 the vertebrate forms, they are accei)ted as the best determinants of the 

 geological age of a bed of rock, even when remains of l)oth kinds are 

 found together. Inverteljrate life, too, appeared on the globe far earlier 

 than vertebrate, antl remains of certain s]iecies are aliundant in the 

 lowest "oldest" of our stratified rocks. 



In the alcoves of the hall is the general collection of meteorites, 



which is one of the largest and most reiiresentative in this 



country, containing as it does specimens from about five 



hvnulred of the seven hundred falls and finds that are known throughout 



the world. Some of tlie princi|Kil features of our collection are: 



Two thousand or more individual masses from the "stone shower" 



