420 A. W. GRABAU PALEOZOIC DELTA DEPOSITS OF NORTH AMERICA 



from the Eden beds of the Cincinnati group. 29 The Trilobite Trinucleus 

 concentricus occurs in the Upper Trenton limestone of New York, but it 

 is even more abundant in the Pulaski shales occurring, according to Hall 

 (Paleontology of New York, volume I), in the highest beds at Pulaski 

 and Lorraine. Rafinesquina squamula James was originally described 

 from the Lorraine (Maysville) beds of the Cincinnati region, where it 

 abounds in the Fairmount bed. Schuchert gives this as the only horizon 

 and locality, but Nickles also lists it from the Southgate or middle mem- 

 ber of the Eden. 30 Zygospira modesta ranges from the Eden to the 

 Richmond, being also found in the Upper Richmond or Maquoketa of the 

 Upper Mississippi Valley. Finally, Rafinesquina alternata ranges from* 

 the Upper Black River to the Richmond in the Cincinnati region and 

 from the Trenton to the top of the Lorraine in New York. 



These faunas, therefore, show the series in question to be of Upper 

 Ordovicic age (Trentonian of Grabau), but as to the precise correlation 

 there is very little evidence. Stose cites Ulrich as favoring a correlation 

 with the Eden of the Cincinnati section and the Lower Lorraine (Frank- 

 fort) of New York. For such a correlation there is only one species, the 

 Bryozoan Callopora sigillaroidea, the others having a wide range. Still 

 we may accept the Eden age of the beds so characterized, but then it ap- 

 pears that this species is found only in the lower (almost the basal) beds 

 of the 1,200 feet of sandstones. This portion might very well be of Eden 

 age, but that does not imply that the upper beds are necessarily so. In- 

 deed, the fossils show that this is not the case. True, all the fossils found 

 are of wide range, but on the whole they are more characteristic of Pu- 

 laski than of Frankfort age. If, then, we may consider with Ulrich the 

 lower beds as of Eden age on the strength of a Bryozoan, we may with 

 equal propriety consider the upper beds of Upper Lorraine or Pulaski if 

 not Oswego age on the strength of the brachiopod Rafinesquina squamula 

 James, especially since there are no species confined to any other horizon. 

 Furthermore, if the basal beds of a series of strata 1,200 feet thick are of 

 Eden age, the top of that series must certainly be of late Pulaski or 

 Oswego age. 



I must here strongly insist on the inadequacy of all such correlation 

 when unsupported by other than fossil evidence. First of all, the range 

 of rare species is by no means established, and, secondly, we have abun- 

 dant evidence that species confined to certain horizons in one locality 

 may transcend that horizon in another. In the present case, Ulrich's 



29 S. A. Miller : Cincinnati Quart. Jour. Sci., vol. 22, p. 129. 



30 J. M. Nickles : The geology of Cincinnati. Jour. Cincinnati Soc. Nat. History, vol. 

 xx, No. 2, pp. 49-100. 



