Cincinnati Society of Natural History. 



of Eaton, the Clinton is underlaid by at least three feet of a greenish 

 blue shaly rock. A small specimen of Tetradium was found within 

 a foot of the base of the Clinton, thus showing the lower Silurian 

 character of the shale. At Fair Haven the Clinton is underlaid by 

 about eight inches of finely stratified, bluish white, hard rock. 



In this western series of exposures the most noteworthy fact is 

 the occurrence at several localities of blue clay at the horizon of the 

 Belfast bed. Still more important for purposes of correlation is the 

 occurrence in the lower parts of these clays at West Milton and 

 Enterprise of Lower Silurian fossils, while Lower Silurian fossils 

 occurred in the shales south of Eaton and in limestone at the very top 

 of the blue clayey shales at Lewisburg and at Fair Haven just beneath 

 the Clinton. When, therefore, the Belfast bed is followed around 

 the northern margin of its area of outcrops to the western outcrops in 

 Ohio, it is found in the western sections to contain Lower Silurian fossils. 



Another feature appears to speak strongly for the Lower Silurian 

 character of the Belfast bed, and that is that it in many exposures is 

 underlaid by a softer, more clayey shale, and this in turn by blue clay,and 

 that either in the shale or in the blue clay undoubted Lower Silurian 

 fossils occur ; moreover it is manifest that above these fossiliferous 

 layers the clayey beds are becoming firmer and more massive, without 

 any time break being indicated in any way until the Clinton is reached, 

 so that the Belfast bed must be considered a part of the Lower Silu- 

 rian, in spite of the occurrence of the Haly sites catemdatus, at least 

 until more satisfactory evidence of its Upper Silurian character can 

 be produced than is possible at present. It is certain that in 

 following the undoubted Belfast bed westward, it merges into more 

 clayey beds which in certain localities are undoubtedly Lower Silurian. 



The occurrence of Halysites catenulatus under these circumstances 

 is interesting. It is an early forerunner of the Upper Silurian in 

 rocks still Lower Silurian. Migration of ocean faunas must have 

 been one method by means of which various horizons have come into 

 existence. The new faunas could hardly have always been the result 

 of developments in situ. In fact, the more abrupt the change of 

 fauna to fauna, the more imperative the supposition that immigrations 

 of faunas had taken place, while development of new types of faunal 

 life in situ should make a demarkation of horizons much more diffi- 

 cult. See in this connection page 397 of Proc. of Boston Soc. Nat. 

 Hist, for May 1, 1889. 



