THE CARBONIFEROUS SYSTEM. 101 



17. Nautilus. — A small, undetermined, compressed, discoidal species, with the very 



narrow periphery truncated. 



18. Nautilus. — A large, sub-discoid, undetermined species, with an open umbilicus, 



and only slightly embracing volutions, that are somewhat wider transversely 

 than, dorso-ventrally, and provided with a row of obscure nodes around, near 

 the middle of each side. Very nearly allied to N. spectabilis, M. and W., from 

 the Chester group, but more compressed, and having narrower and apparently 

 one or two more volutions. Specimens mere fragments. 



In his letter Prof. Meek adds : 



" From these fossils it is clearly evident that the limestone from which they were 

 obtained, belongs to the horizon of the Lower Carboniferous limestone series of the 

 "Western States. They also show that it does not belong to any of the inferior mem- 

 bers of that series. 



" Of the eighteen or twenty species of fossils sent me from this rock about one-half 

 are represented in the collection only by specimens that are too imperfect for specific 

 identification; though none of them, so far as their characters can be made out, ap- 

 pear to be allied to known forms from any horizon below the St. Louis limestone. 



" Of the remaining species, five can be identified confidently with Chester forms, 

 and three others are either identical with Chester species, or most closely allied to 

 forms of that age. Hence we may safely say that eight of the species are Chester 

 types. Two, however, seem to be identical with species described from the St. Louis 

 limestone further west. 



" From these facts I can scarcely doubt that we have in these local masses of lime- 

 stone a representation of the Chester group of the Lower Carboniferous limestone 

 series ; though it is possible that there may also be some representation of the St. 

 Louis limestone of the same series at some of the outcrops. 



"The discovery of these beds is, I believe, the first indication we have had of the 

 existence of any member of the Lower Carboniferous limestone series of the West in 

 Ohio. They also seem to show that the old Carboniferous sea did not extend to this 

 region during the deposition of any but the later members of the lower limestone 

 series, although we know it had done so previously, that is, during the older Waverly 

 period." 



The last remark of Mr. Meek requires a little qualification or explana- 

 tion, for inasmuch as the Waverly group is stratified, it is evident that 

 all its layers were deposited in water ; and as many of its fossils are iden- 

 tical with those found in the Carboniferous limestones of the South-west — 

 and they are of marine origin — we may be sure that this water was the 

 sea. But these mechanical sediments are shore deposits, and not such 

 as accumulate in the deep basins of the open sea. Much of the Waverly 

 group is composed of coarse sandstone, and, as we have seen in southern 

 and middle Ohio, it contains heavy and extensive sheets of conglomerate, 

 the product of shore waves. Hence, in the relations of the calcareous 

 and mechanical sediments which make up the Lower Carboniferous for- 



