NOTE 



The results here given are of investigations by Prof. Orton 

 carried on during the season of 1897 at the instance of the 

 late Prof. James Hall, state geologist and paleontologist, and 

 were communicated with the annual report of that year; but it 

 has since been judged wise, in view of the far-reaching im- 

 portance of this paper and in order to secure its wider diffusion, 

 to issue it separately as a museum bulletin. The paper is there- 

 fore appended to the museum report for 1899. 



In references, volume and page numbers are separated by a 

 colon; e. g. 16: 467 means vol. 16, p. 467. 



John M. Clarke 



