Cincinnatian and Lexington Fossils 69 



fold are distinctly less conspicuous and placed lower. Shells of this 

 type appear to grade into Platystrophia cypha. Both shells with 

 acute postero-Iateral outlines, as in case of Platystrophia acutilirata, 

 and shells with rectangular postero-Iateral outlines are present, for 

 instance at Madison, Versailles, and Bull creek, Indiana. 



In the other type of shell found in the Waynes ville bed (plate 

 iii, figs. 3, 4), the fold is lower, the plications on the fold are more 

 nearly of equal size, the shell is broader than in Platystrophia in- 

 flata, but the postero-Iateral outline is approximately rectangular or 

 but moderately acute. Specimens of this type grade into a form 

 with relatively few plications, and somewhat resembling Platystro- 

 phia laticosta. Specimens of this type occur at Concord, Ken- 

 tucky; Fort Ancient, Oregonia, and Waynesville. Ohio; and at 

 Versailles and Madison, Indiana. Some of the specimens at Con- 

 cord, Kentucky, resemble Platystrophia intiata in outline. 



With numerous specimens from all horizons and from widely 

 separated localities in Ohio, Indiana, and Kentucky at hand, it has 

 been found impossible to determine the exact line of derivation of 

 Platystrophia acutilirata. Much remains to be done. Future 

 work will require a study of Platystrophia by faunal associations, 

 its range of variation within those associations, and the spread of 

 these variations along with the general associated faunas, geo- 

 graphically as well as vertically. The collection of prodigious 

 quantities of specimens from some large vertical section is a valu- 

 able factor in such a problem, but in itself is insufficient to solve 

 the complicated problem involved. Owing to the enormous amount 

 of material which could be readily collected, the line of development 

 of the various forms of Platystrophia will remain an interesting 

 problem for a long time. The admirable studies by Prof. E. R. 

 Cumings are classic. The notes here presented are merely an at- 

 tempt to call attention to some of the species and varieties present 

 in the area of the Cincinnati geanticline in such a manner as to 

 give a little more definiteness to some of the names commonly used 

 or almost forgotten. 



Clitambonites rogersensis, Foerste. 



A comparison of Clitambonites rogersensis from the Rogers 

 Gap division of the Economy bed, at Rogers Gap, Kentucky, with 

 typical specimens of Clitambonites diversus, Shaler, has shown that 

 the Kentuckian form is more distinct than at first supposed. The 



