FOSSIL AQl'MnCM 109 



reasons the (Mionuous Noluinr of food iicccssai-y to siii)i)oi-t it could not. he 



luaintaiiUMl within its raiij;v of sea. 



In tlie first ah'oxc to the left, hy tlic window, is a "fossil 

 Fossil . ,, . , . , , ■ I I ■• 1 I- 



. . aiinarnnn ni wlncli a nunilxM- ol models ol these earliest 



Aquarium _' 



fishes are arran<i'e(l in a j^'roup, as though alive in the sea. 



In the next alcove are the early fossil sharks which superseded the 

 tribe of i)lated fishes just mentioned. These sharks had soft skeletons, 

 „, , simple fins and a number of other primitive features which 



lead to the belief that all of the higher fishes, and the higher 

 baek-boned animals therefore as well, were descended from them, their 

 simpler structures becoming more complicated in many directions. In 

 one of the early sharks here exhibited, impressions of soft parts such as 

 muscles and gill filaments have been preserved. 



In the third alcove appear rare fossils of silver sharks or Chimteroids, 

 which appear to have been developed from a primitive race 

 of sharks. Curiously enough fossil egg capsules of these 

 forms are sometimes preserved, and examples are here present. In neigh- 

 boring cases are shown ancient lungfishes and ganoids — groups from 

 which all land-living quadrupeds are believed to be descended. 



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



waters during the Age of Reptiles. They were of many 



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



of bone, with enamelled surface. One of the few survivors {Amia) of this 



ancient group is here shown living (in a window aquarium), to give the 



visitor a clearer idea of the fishes of the "Middle 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 Palaeontology 



Turning northward at the center of the Quaternary Hall containing 

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

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

 tology. Owing to important changes in progress in the arrangement of 

 this hall, but a portion of the collections are at present on exhibition, though 

 all are available for study. 



