June, 1916] The Ordovician- Silurian Boundary 335 



the Richmond-Upper Medina break as failed to pass the 

 Maysville-Richmond break. 



Retaining, then, the Ordovician-Silurian boundary at its 

 old and generally accepted position between the Richmond and 

 the Upper Medina, a slight refinement may be made in the 

 drawing of the boundary in Ohio. 



The Richmond has been considered as ending with the 

 Belfast* beds, a series of strata developed in Ohio along the 

 east side of the Cincinnati dome. They are generally barren of 

 fossils, and chiefly on the basis of rather common annelid 

 remains have been classed as Ordovician, despite the finding 

 of Halysites catenularia and Orthis flabellites in them. But 

 during the past season there have been added to these Dal- 

 manella elegantula and var. parva, Rhynochonella janea and 

 Hormotoma sublata, all found near Lawshe and near West 

 Union, Adams County, Ohio. 



Disregarding the annelid remains, which cannot be used in 

 correlating anything, the total fauna of the Belfast is Brassfield 

 (Upper Medina) in its affinities. 



The Ordovician-Silurian boundary of Ohio, Indiana, and 

 Kentucky should be drawn, then, at the top of the next under- 

 lying beds, the Elkhorn and its equivalents. 



* Foerste, Jour. Cin. Soc. Nat. Hist., Vol. XVIII, Feb., 1896, pp. 161-199. 



Miami University. 



