674 GEOLOGY OF OHIO. 
terminated in its being assigned, without dissent, to the Niagara series. _ 
It forms the crowning member of this series in the northern and western 
portions of its widely extended field. It has received the names of vari- 
ous localities where it is distinctly shown, being styled the Guelph forma- 
tion in Canada, the Racine beds, or Milwaukee beds, in Wisconsin, and 
the Bridgeport beds in northern Illinois. In southern Ohio no local 
name can be selected so appropriate and free from ambiguity as the 
Cedarville limestone, constituting, as it does, the only member of the 
Niagara series shown in the extensive quarries opened at this village. 
There is not, however, as great a thickness of the limestone shown at 
Cedarville as at Yellow Springs. The exposure of the Niagara rocks at 
this last named place has been repeatedly referred to, and now, since all 
the elements that enter into it have been given, a somewhat more 
detailed account will be supplied. It is decidely the best section of the 
Niagara series shown in Greene county, and is but little inferior to the 
section at Holcomb’s lime-kilns, below Springfield. 
The Clinton limestone follows up the Yellow Springs Branch to a point 
nearly opposite the extensive quarries of W. Sroufe, Esq. Starting from 
this well-settled base, eighty-four feet of the Niagara rocks are traversed 
in a very steep ascent. The uppermost thirty feet are shown in the 
quarries before referred to; the lowermost thirty feet are well shown in 
the adjacent banks of the Cascade Branch. Exposures of the intervening 
beds are not wanting in the immediate vicinity. The thickness here 
given is thus divided: 
Cedarville bedsersc ssc ute ction ate cssniocdsacocstlecssnctucleaecscnettecasneectoonens 22 feet. 
Hpringhield Stone irwces\nos sesesecees ceoscsencansteansnnees aicewets Jaduesenthabaduines 24 ** 
West! Onion elittins cooly icike csalcaissuatnon acces nceenciss eae pneel estore esters Bian 
Niagara SMAleg picsseosssescdsusnssisccosssocledes col ccassieccactesscinceetcincenmiss cee sseeees SO lin 
Dota wes saecceeicdecee ie sseb ea aie Pets fous do cslaletets ain uirelatem cae asa 84 “ 
The twenty-two feet of the upper division are further re-enforced in the 
higher ground adjoining the ravine. It gains ten feet, at least, in the 
land immediately to the westward, and may be safely taken as not far 
below forty feet in its total thickness here. 
The identification of this stratum has been made complete by the dis- 
covery of a considerable number of fossils in it that are peculiar to the 
above named horizon. A list of a dozen or more of these forms common 
to the Guelph and the Cedarville beds is given in the reports of Highland 
and Clarke counties. Of these the most prominent and characteristic 
are two great shells, the enormous and somewhat abnormal brachiopod 
Trimerella, and a lamellibranch shell of even greater bulk, Megalomus 
Canadensis. Trimerella is represented in these beds not only by the 
