150 Evolution and Distribution of Fishes 



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Fig. 18. Elonichthys bro-zcni. — i ; outline restoration of fish, 

 one-half natural size; 2, 3, two t3pes of flank scales; 4, ridge scale; 

 all enlarged: 5, portion of dorsal fin-rays and marginal fulcra; 6, 

 portion of rays from base of dorsal fin. (All reduced from Lambe). 



the Pennsylvania, New York, Ohio, Illinois, Iowa and 

 other State Surveys. In several of these also, bone or 

 "fish-beds," that vary from one to several inches in thick- 

 ness occur. Lesley frequently refers to these in Pennsyl- 

 vania. But the most noteworthy probably are four thin and 

 apparently marine beds that have been studied by Newberry 

 and Worthen in the Burlington zone of Illinois {g8 : 12). 

 One of these, in which the teeth and spines of fishes are em- 

 bedded in great numbers "stretches at least from Quincy, 

 Illinois ... to Augusta in Iowa," points nearly a 

 hundred miles apart. This indicates that the cause which 

 produced such general destruction amongst the vertebrated 

 animals of this period was not local, but operated simultane- 

 ously over a wide geographical area. 



To the writer it seems that such an area, at least 10,000 

 square miles in extent, and continuously covered with the 

 remains of fishes that were however of freshwater 

 ancestry, supplies the best possible explanation for origin 

 of the Illinois oil beds. The soft perishable oily parts 



