66 -^'ig- P- Focrsfc 



species uiKfiiestionably is from some horizon in the Richmond 

 group, and since no part of the Richmond is exposed in the im- 

 mediate vicinity of Louisville, it is evident that his type must have 

 been obtained from some other locality. 



It is customary to identify as Platystrophia acutilirata the 

 Whitewater form which is so abundantly exposed at Richmond, 

 Indiana, and at corresponding horizons in Ohio and Indiana. This 

 view is favored by the ventricose appearance of the body of the 

 shell, mentioned in the original description and indicated in the 

 accompanying figure; also by the acute hinge extremity and by the 

 relatively considerable number of lateral plications. In the original 

 description 32 lateral plications are mentioned which would result 

 in 16 plications on each side of the fold. In the accompanying 

 figure, 12 plications are represented on one side and 14 on the other 

 side of the fold. 



As a matter of fact, however, the \\diite\vater bed does not 

 appear to be exposed nearer than Versailles, Indiana, and the Lib- 

 erty representatives of this type of Platystrophia rarely have more 

 than II lateral plications on each side of the fold, although such 

 specimens do occur occasionally, but even then the number does not 

 equal 14 or 16. The Liberty bed, however, is abundantly exposed 

 at numerous localities within 30 miles of Louisville, and is riclily 

 fossiliferous. 



Specimens with numerous lateral plications occur also at 

 numerous localities in the Arnheim bed west of the Cincinnati 

 geanticline between the Ohio river and Lebanon, Kentucky. One 

 of these localities, south of Salt river on the road from Louisville 

 to Bardstown, was along one of the chief lines of travel at the time 

 Conrad wrote his description. The s]iecimens of Platystrophia 

 found here (plate iv, figs. 7 A,B, 14 A,B) are characterized by the 

 prominence of the fold, the depth of the sinus, the sharpness of the 

 plications, die acute lateral extremities, and by the antero-lateral 

 compression of these extremities which gives them a wing-like 

 rather than spine-like appearance. The number of lateral plications 

 on each side of the fold frequently is 11, and sometimes equals 14. 

 Similar shells, found in the Arnheim along the same line of travel, 

 one mile south of Mount Washington, are more ventricose, and 

 occasionally have more spine-like projections of the shell along the 

 hinge-line, and numerous lateral plications, but only in case of 

 selected specimens. 



