REVIEWS 475 



rocks in Ohio outcrop in three districts, the most extensive of which is a 

 belt with an average width of ten to twelve miles extending from the Ohio 

 River across the central part of the state to the islands in Lake Erie, north 

 of Sandusky, although the limestones do not extend south of Pickaway 

 County. The second district, in the vicinity of Bellefontaine, is in the 

 western part of the state; while the third is a somewhat crescent-shaped 

 area in the northwestern part of the state, sweeping around from the Michi- 

 gan line to that of Indiana. 



The second chapter, which is devoted to a "Discussion of Sections and 

 Faunas," contains a large number of sections of the formations under con- 

 sideration in Ohio with lists of their fossils. The Columbus and Delaware 

 limestones of Central Ohio have been subdivided into thirteen zones which 

 are indicated by letters ranging from A, which represents the basal con- 

 glomerate of the Columbus limestone resting on the Monroe limestone, up 

 to M at the top of the Delaware limestone. Each zone is fossiliferous, with 

 the exception of the lowest one, or Zone A, and following the lithologic 

 description of each one is a list of the fossils common to the zone. In 

 regard to correlation with the standard formations of New York, the con- 

 clusion is reached that the Columbus limestone represents the Onondaga 

 limestone and the Delaware limestone, and Olentangy formation the 

 Marcellus shale and Hamilton beds of that state. 



In chapter iii "The Relationships of the Middle Devonian Faunas of 

 Ohio" are very fully discussed and it is shown that the Columbus fauna is 

 composed of two elements, one of which came from the north and the 

 other from the south. The last chapter is devoted to "Notes on and 

 Description of Species," in which twelve new species and one variety are 

 named and described. 



The bulletin is illustrated by seventeen plates, thirteen of which give 

 views of characteristic portions of the formations described. One is a 

 "Hypothetical Map of the Middle Devonian Sea during Columbus Time" 

 and another of the same sea "During Delaware-Olentangy Time." The 

 last two plates are illustrations of fossils showing the new species which 

 were drawn by Miss Edith Hyde. 



The bulletin as a whole gives a scholarly account of the Middle Devonian 

 formations of Ohio and contains a larger amount of information concerning 

 them than any other published work. From a geological standpoint it is 

 an interesting and valuable bulletin ranking among the best published by 



the Geological Survey of Ohio. 



C. S. P. 



