No. 556] SHORTER ARTICLES AND DISCUSSION 247 



have three families of fishes represented: (1) Coccosteidse ; (2) 

 Rhizodontida? ; (3) Diplacanthida?. The genera and species can 

 not be precisely determined. 



These fish remains, taken by themselves, would certainly be 

 regarded as Devonian. Walcott's Ordovician species from 

 Canon City were said by Professor James Hall to have such a 

 Devonian facies that lie would certainly have referred them to 

 the Devonian, but for the accompanying invertebrate fauna. 



In general, when there is a conflict between the evidence 

 from vertebrate and invertebrate fossils, the vertebrates must 

 be allowed the most weight ; but it is evident that the numerous 

 and varied Devonian fishes had ancestors, so it is to be expected 

 that types more or less like those of the Devonian will be found 

 in older rocks. I understand from Mr. Worcester that there 

 is no reason to believe that the Silurian is represented in the 

 locality. 



Schuchert ("Paleogeography of North America") remarks 

 that in the Ordovieie or Ordovician, duringthe retreat of the sea, 



The first evidence of those peculiar heavily armored fishes belonging 

 to the ostracodernis appears in cleanly washed beach sands and less 

 abundantly in dolomites at three widely separated places in Colorado 

 and Wyoming. They are now all fragmentary and seem to have been 

 washed into the sea by the rivers. From this can it be inferred that 

 during some earlier inundation the marine ancestors of these fishes were 

 retained upon the- land in relict seas, and under the stress of evanescent 

 waters became modified into the armored double-breathing animals that 

 gave rise later to the true fishes? Such being the interpretation, the 

 marine fishes must then have been derived from land [freshwater] 

 fishes, as suggested by Chamberlin and Salisbury. 



The two localities in addition to the famous one at Canon City 

 are (Dr. Eastman in litt.) in the Big Horn Mts., and in the 

 Black Hills uplift, in a bed lying above the Deadwood Forma- 

 tion. Both were discovered by Mr. N. H. Darton. These all 

 agree in the character of their fish remains. 



T. D. A. COCKERELL 



University of Colorado, 

 December 14 



