to DAVENPORT ACAfJEMY OF NATURAL SCIENCES. 



forms described by Professor Hall under other names, but not figured. 

 Until all these have been fully illustrated, it is impossible to make 

 detailed comparison without specimens of all these forms." * 



In the State of Michigan a particular shell abounded to such an ex- 

 tent that the rock containing it took its name from the shell. It was 

 known as the Tropidoleptus bed. Subsequently, Professor Winchell 

 writes: "The term Tropidoleptus beds is changed to Bryozoa beds, 

 since the supposed Tropidoleptus proves to be a Strophodonta, an en- 

 tirely different species." t 



Professor Hall, of the State Geological Survey of New York, has 

 more than once claimed that other paleontologists had entirely mis- 

 understood his descriptions. They had not only failed to identify, but 

 out of fossils he had described they had made new genera as well as 

 species. In the twentieth report on the New York State Museum of 

 Natural History several pages are devoted to such controversy. 



These are representative men — acknowledged authorities in all that 

 pertains to the science of paleontology. Was there ever a more uniform 

 testimony than that which is thus borne to the difficulty of determining 

 species? 



Will not errors increase in proportion to our lack of these oppor- 

 tunities? With limited means, limited time, limited education, limited 

 experience, limited libraries, and limited cabinets of fossils, will not 

 our work show the effect of such limitation? Errors will and must 

 abound. Is this work of identifying two hundred and forty-six species 

 from our few quarries a perfect work? Is this pamphlet an excep- 

 tion to all other writings on paleontology? 



I put in compact shape the points on which I have touched : 



It is improbable that such a number of species should be found in 

 the Corniferous limestone of our vicinity, for these reasons : 



First. Because of the character of the rock. 



Second. Because of our very limited exposures. 



Third. Because their occurrence in such numbers is against the ex- 

 perience of every other worker in our rocks. 



Fourth. Because, in comparison, Cook's quarry and vicinity are 

 made to furnish one and a half times as many species of fossils, and 

 twice as many of a certain species of coral, as have been discovered by 

 the two geological surveys of the State of Michigan. 



♦Geological Report of Illinois, Vol. III., p. 434. 



f Geological Report on the Grand Traverse Region, p. S4. 



