INTRODUCTION. XIII 



if not identical with the New York Oriskany species, R. ovalis, 

 of Hall, is certainly a very closely allied representative species; 

 also, with several undetermined species of Spirifer, some of 

 which are nearly related to S. arctus, Hall, and S. arenosus, 

 Conrad, from the New York Oriskany: and a Striclclandiana, 

 we have not been able to entirely satisfy ourselves is distinct 

 from S. elongata (=Pentameriis elongatus), Vanuxem. In New 

 York, S. elongata is characteristic of the higher Onondaga lime- 

 stone of the Upper Helderberg, but in Canada it is common to 

 that position and the Oriskany sandstone. 



Judging from such an assemblage of fossils as this, and the 

 entire absence, so far as yet known, of any species in these 

 beds peculiar to any lower horizon (although Platyceras Geb- 

 hardi and Eatonia peculiaris are, in New York, common to the 

 "Shaley Limestone" division of the Lower Helderberg group 

 and the Oriskany), we cannot resist the conclusion, that a 

 considerable portion of the cherty limestone forming the upper 

 part of the Clear-creek series, as first understood, belongs to 

 the Oriskany period, and that the line between the Upper 

 Silurian and the Devonian, of this region, should be drawn 

 between these cherty beds and the strata below, equivalent to 

 those from which we collected the Lower Helderberg fossils at 

 Bailey's Landing. Exactly how far down in the series this 

 line should be carried we are unable to say, as we found no 

 abrupt lithological change, and we saw no fossils near the 

 horizon of the probable junction. From all the facts, however, 

 we are led to believe that possibly as much as two hundred 

 feet, and perhaps more, of these beds should be included in the 

 Oriskany. 



In the sandstone immediately overlying the cherty beds, 

 near Jonesboro', Union county, we found the following fossils (or 

 more properly their moulds — the fossils themselves being, in all 

 cases, dissolved out so as to leave empty cavities), viz : A small 

 Zaphrentis, Pleurodictyum problematicum, Goldf.; an Orthis like 



