116 CI AST FOSSIL SIIAh'K 



fact, Dinichthys, shown in the middle of the j!;allery, was i)robably 

 anions the most dcstnictivc (Tcaturcs that ever hved in the sea. Its 

 jaws were so stron*:; that it could crush a plate of bone as tliick as one's 

 hand. Such an actual speciuien, fra(;tured in life and sliowin*; the 

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



The collection is so arran^jed that he who makes the tour can see the 

 l)rinci])al kinds of fossil fishes and is able, in a measure, to outHne the 

 history and j)edi<;ree of the entire grou]). He can trace the rise and fall 

 of the early |)late-covered fishes; tlie era of the sharks which on the one 

 hand supplanted the earliest fishes and were in time replaced by the more 

 efhcient lun«;fishes and ganoids; the age of ganoids when the waters were 

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

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

 whose methods of swinnning, feeding and breeding are far more efficient 

 than those of any of their predecessors. 



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



huge fossil shark in which the actual teeth are arranged as 



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



Giant Fossil ,•,,•, • i ^ ■ r 



gjj^j.j^ teeth ni 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 probably 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 



a(iuarium" in which a number of models of these earliest 

 Aquarium i i i- • i 



nshes are arranged m a group, as though alive in 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In the next alcove are the early fossil sharks which superseded the 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 



Sharks 



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



l)ack-b()n(Ml animals therefore as well, were descended from them, their 



simpler structures becoming more coin]:)licated in many directions. In 



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



muscles and gill filaments have ])een preserved. 



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



which appear to have been developed from a primitive race 



of sharks. Curiously (Miough fossil egg capsules of these 



forms are sometimes ])reserve(l, and examples are here present. 



In neighboring cases are shown ancient lungfishes and ganoids — 



grou])s from which all land-living (iuadru})eds are believed to be 



descended. 



