Ai^c of the Pt. Pleasant Beds. 95 



Kentucky. A study of the rocks at Maysville, and of the fos- 

 sils contained therein, led him to refer them to the Hudson 

 River Group of New York. He said that neither the charac- 

 ter of the rocks nor the fossils indicate the Trenton Group. 

 He described a .section as seen at Cincinnati, and concluded 

 upon the evidence of Tria) llnus bcckii and fossils in the 

 overlyinjT rocks, that the Utica slate was represented ; and 

 that althou^Hi a lower rock was exposed, it niij^ht (^r might not 

 be the Trenton. He then descril)es the overlying .series form- 

 ing the main mass at Cincinnati, concluding that they repre- 

 sent the Hudson River Group. The remains of /sW^/z/.v [Asa- 

 phiis) had usually been considered sufficient proof of the 

 identity of the Cincinnati rocks with tho.se of Trenton age in 

 New York, but Hall said that all the specimens he had seen 

 were different from Trenton forms. " So that," he continues, 

 " although certain species of the genus do occur in the Tren- 

 ton limestone and are characteri.stic of that formation, others 

 are not necessarily so, and unless we take wide ranges in our 

 groupings, we can not depend on generic types In this case 

 the amount of evidence seems to be about equally divided be- 

 tween the Trenton and Hudson River Groups ; but since there 

 are fossils decidedly typical of the latter, and we know that in 

 New York they never occur in a lower position, we are com- 

 pelled to admit that this formation is of the .same geological 

 age."* 



In all the subsequent publications of Prof. Hall, this term 

 has been applied to the rocks of this age in the Missi.ssippi 

 Valley. He has been followed by mo.st of the writers who 

 have referred to the rocks up to the year 1865. In this year 

 Meek and Worthen proposedf the name "Cincinnati Group " 

 to cover the strata of Ohio and other western States, pre- 

 viously referred to the " Hudson River Group." The term 

 "Cincinnati Group" has, since its proposal, been generally 

 u.sed, especially by western geologists, as they recognized it 

 as a convenient and applicable term. Its employment has, 

 however, always been resisted by Hall and some others, who 

 continue to use Hudson River and Utica Shale. We are not 

 now concerned with the application of any special term, being 



*Ibid, page 276. 



tPliil. Acad. Nat. Sci. I'roc, vol. 17, 1865, page 155. 



