340 Foerste — Ordovician-Siluriaii Contact in the 



until much better representatives of the type species are 

 secured. Sphaerexochus pisum is a species of Deiphon and 

 is closely related to I). forbesi. Representatives of genera 

 more abundantly represented in the Ordovician occur in the 

 Clinton, such as Platystrophia daytonensis, PI. reversata, 

 Hebertella fausta, IT. daytonensis, Gyclonema daytonensis. 

 A form of Plectambonites allied to PI. sericea is the only 

 species passing from the Ordovician into the Clinton with 

 little change ; the more distinct form, PI. transver satis, how- 

 ever, is much more common. The identification of the lowest 

 Silurian bed in the area of the Cincinnati geanticline as Clinton 

 does not rest so much upon the identity of faunas at the two 

 localities as upon the presence of a few species which are iden- 

 tical, a few which are closely allied, the general absence of 

 species which may be regarded as most typical of the Roches- 

 ter shale of New York, and a general facies which suggests 

 that the western fauna represents a somewhat similar stage in 

 development. 



In New York, some of the species, which in the area of the 

 Cincinnati geanticline are not found beneath the Osgood bed, 

 occur in the lenses at the top of the Clinton ; some of them 

 occur even in the upper beds of the Clinton. As far as may 

 be determined from the evidence at hand, the Osgood bed con- 

 tains a part of the fauna of the lenses at the top of the Clinton 

 and of the lower half of the Rochester shales in New York, a 

 part of this fauna beginning at the top of the Clinton in that 

 state ; while the Clinton of Ohio, Indiana, and Kentucky appears 

 to have attained the stage of development equivalent to that 

 of the Clinton of New York, below the lenses, but does not 

 contain such species as Pentamerus obiongus, Atrypa reticu- 

 laris, Spirifer radiafa&s, Sp. niagarensis, which in the west 

 begin their existence in the Osgood bed. The faunal elements 

 of the Clinton in the two areas are different and a more exact 

 comparison is at present impossible. 



Lists of Niagaran Fossils. 



The best lists of the fossils of the various subdivisions of the 

 Cincinnatian strata in Ohio, Indiana, and adjacent Kentucky 

 are those published by Mr. J. M. Nickles in the Journal of the 

 Cincinnati Society of Natural History, volume xx, No. 2, 1902. 



A list of the fossils identified from the Clinton of Indiana 

 was published in " Silurian and Devonian limestones of Ten- 

 nessee and Kentucky," a Bulletin of the Geological Society of 

 America, in 1901, on pages 438-411. 



Osgood Fossils. 

 In the following list the names of the localities Osgood, New 

 Marion, and JBig Creek are indicated by the letters O, N, and 

 B following immediately after the name of the species. Unless 



