116 (IJAXT FOSSIL SHARK 



fact, Dinichthys, shown in the middle of the gallery, was probably 

 among the most destructive creatures that ever lived in the sea. Its 

 jaws were so strong that it could crush a plate of bone as thick as one's 

 hand. Such an actual specimen, fractured in life and showing the 

 marks of "teeth" is shown in a neighboring case. 



Th(> collection is so arranged that he who makes the tour can see the 

 principal kinds of fossil fishes and is able, in a measure, to outline the 

 history and pedigree of the entire group. He can trace the rise and fall 

 of the early plate-covered fishes; the era of the sharks which on the one 

 hand supi)lanted the earliest fishes and were in time replaced by the more 

 efficient lungfishes and ganoids; the age of ganoids when the waters were 

 filled with these enamel-scaled fishes; finally th(> age of the bony-fishes, 

 or teleosts, the nniltitudinous forms of to-day, the herrings, cods, perches, 

 whose methods of swimming, feeding and l)r(>eding are far more efficient 

 than those of any of their ])redecessors. 



Above the entrance are the jaws "models", spreading nine feet, of a 



huge foss'l shark in which the actual teeth are arranged as 



jaws o j^^ ^j^^^ sharks of to-day, in the usual banks or rows — the 



Giant Fossil , • , , • , • , , • ^ 



gjjgj.jj teeth m the hmder rows servmg to replace those m front, 



nature having dealt more kindly in the matter of teeth 



with sharks than with man. Such a shark j^robably measured from 



seventy to ninety feet and its race may well have become extinct, when 



for various reasons the enormous volume of food necessary to support 



it could not be maintained within its range of sea. 



In the first alcove to the left, by the window, is a "fossil 



aciuarium" in which a numfjer of models of these earliest 

 Aquarium i i i- • i 



fishes are arranged m a group, as though alive m the sea. 



In the next alcove are the early fossil sharks which superseded the 



tribe of plated 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 



back-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 \\\c third alcove appear rare fossils of silver sharks or Chima;roids, 



. which api^ear 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 neighboring cases are shown ancient lungfishes and ganoids — 



groups from which all land-living quadrupeds are believed to be 



descended. 



