FOSSIL FISHES 87 



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

 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 arc shown ancient lungfisb.es 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- 

 Tplsosts 



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 Palaeontology. 

 At the entrance of the hall there is a large slab of fossiliferous limestone 

 from Kelleys Island in Lake Erie near Sandusky, whose surface has been 



smoothed, grooved and scratched by the stones and sand in 

 G the bottom of the vast moving ice sheet or glacier that covered 



the northeastern part of North America during the Glacial 

 Epoch. The front of this continental glacier is now thought by most 

 geologists to have retreated northward across Lake Erie from 30,000 to 

 50,000 years ago. At Kelleys Island, the ice was moving from east to west. 

 Just beyond the glacial groove specimen, the visitor will see an exhibit 

 illustrating some of the results of an expedition which the Museum sent to 

 Martinique and St. Vincent during the great volcanic eruptions of 1902- 



1903 that devastated those islands of the Lesser Antilles chain. 

 B , A set of four relief maps shows the island of Martinique and its 



famous volcano, Mont Pelee, at three important stages of the 



