98 PROCEEDINGS OF THE PHILABELPHIA MEETING 



except in certain limited areas wliere it is underlain by similar Devonian stiale, 

 the lithologic break is conspicuous. This break, moreover, marks a strong 

 transgression unconformity which brings the Chattanoogan in contact with 

 many widely differing older formations, ranging in age from Ordovician to 

 late Devonian. The recent tendency to limit the Mississippi in Ohio and 

 adjacent States at, or at an horizon supposedly corresponding to. the base of 

 the Bei-ea sandstone is regarded as impractical and generally impossible, ex- 

 cept in Ohio, and as inharmonious with long-established practice in the Mis- 

 sissippi Vallej' and in New York. This imperfectly considered effort would 

 subordinate a highly important and perhaps universally recognizable dias- 

 trophic boundary to one that is but locally definable and on the whole of 

 greatly inferior taxonomic significance. 



(j. The Louisiana limestone in Missouri and the Chonopectus sandstone at 

 Burlington, Iowa, are underlain by gray or black shales which have been and 

 are yet commonly x'eferred to the basal j)art uf the Kinderhookian series. 

 These basal shales correspond in position with the Cleveland and Huron shales 

 of Ohio, and on this ground alone may be correlated with them. 



7. In Missouri these basal shales contain fossils. None of the species are 

 of unquestionable Devonian types. On the other hand, a large proportion of 

 their number, especially of the invertebrates near the top, is identified with 

 otherwise t.vpioal Louisiana limestone species. The shale contains also re- 

 mains of fish which are closely allied to, and perhaps in part identifiable with. 

 Huron shale species. Fossils occur in these shales also at Burlington. Here 

 they have a more decidedly Mississippian aspect than pertains to the succeed- 

 ing Chonopectus fauna. 



8. Remains of Arthrodirian fishes, especially Dinichthys, occur at different 

 horizons in the Chattanoogan series, the first being near the base, the last at 

 the very top. The last being unquestioned Mississipjiian. it follows that 

 Dinichthys, at least, is not confined to Devonian formations. Indeed, the evi- 

 dence in hand indicates that most of the genera of fishes found in Upper 

 Devonian rocks range upward into the Mississippian. None of the Chatta- 

 noogan fishes, however, are specifically identical with any of those found in 

 undoubted Devonian rocks. 



r>. The evidence of the plants is much the same in tenor as that of the 

 fishes; but here it seems that at least one long-ranging (Genesee and Portage) 

 species passes without recognizable modification into the lower part of the 

 Chattanoogan. This apparent Devonian alliance, however, is offset by another 

 plant which unites these lower Chattanoogan beds with one at the extreme 

 top of the series, which all agree is of Mississippian age. Only a few plants 

 are as yet known from the Chattanoogan series. With the exception of the 

 first (Pseudohoniia inornata) and possibly another, all of the species are con- 

 fined to this series; or, if represented elsewhere by identical or closely allied 

 forms, these occur in beds that are either definitely known to be of post- 

 Devonian ages or in deposits about which geologists have differed as to whether 

 they should be called Devonian or MLssissippian. 



10. Minute teeth and plates, known as conodonts, are rather generally dis- 

 tributed in the black shales of the Chattanoogan series and are doubtless the 

 most abundant of its fossils. American authors commonly have compared 

 these with the conodonts of the Genesee shale described by Hinde, forgetting 



