THE 



Ohio Journal of Science 



PUBLISHED BY THE 



Ohio State; University Scientific Society 

 Volume XVI JUNE, 1916 No. 8 



TABLE OF CONTENTS 



Shideler — The Ordovician-Silurian Boundary 329 



Reed — The Epibranchial Placodes of Squalus Acanthias 386 



HoRSFALL — Additions to the Jassoidea of Missouri 354 



Price— Starch in Apple Trees 356 



SCH AFFNER — A General System of Floral Diagrams 360 



THE ORDOVICIAN-SILURIAN BOUNDARY. 



W. H. Shideler. 



Of late there has been an increasing disagreement as to just 

 where the Ordovician-Silurian division should be drawn, and 

 there has developed a strong movement toward shifting the 

 division plane from its old and commonly accepted position 

 at the Richmond-Albion (Upper Medina-Brassfield or "Ohio 

 Clinton") break, down to the Maysville-Richmond break, thus 

 incorporating the whole of the Richmond into the Silurian. 



The shift in boundary is proposed* primarily for the following 

 reasons, to express them briefly: 



1. Only about 5% of the Maysville species are common to 

 the Richmond, and these are nearly all generalized and long- 

 lived types, while the Richmond introduces twenty new generic 

 and four new family types; while all of the Bryozoa, Echino- 

 dermata, and most of the corals, trilobites and brachiopods 

 are strikingly different. 



2. The Ordovician relationships of the Richmond are 

 neutralized by an equally strong Silurian tendency when 

 compared with the Silurian. 



*E. O. Ulrich. The Ordovician-Silurian Boundary. Etude faite a la XII. 

 Session du Congres geologique international, reproduite du Compte-Rendu. 



329 



