68 A^(S- f"- Pocrste 



plate 35, fig". 4) corresponds essentially to typical Platystrophia 

 acutilirata of Conrad and Meek. Figures 4 a-c on the same plate 

 correspond to the variety inflata of James. 



Platystrophia annieana, James, consists of shells evidently be- 

 longing to the typical Platystrophia acutilirata group, but differing 

 m having the lateral margins convex rather than concave. The 

 tendency toward a spine-like prolongation of the shell along the 

 hinge-line, in other words, is missing. Viewed directly from in 

 front, these shells appear more evenly convex, and less ventricose 

 centrally. The number of lateral plications varies from 12 to 16 

 on each side of the fold. Specimens of this type occur at various 

 horizons, but only as selected specimens, and not in sufficient num- 

 bers to suggest more than individual characteristics. James's types 

 (No. 84, James Collection, Walker Museum, Chicago University) 

 were secured in the upper part of the Waynesville bed, at Blan- 

 chester, Ohio. (Plate vi, figs. 14 A-C.) 



Typical Platystrophia~ acutilirata is characterized by the low, 

 broad, rounded fold, with four plications of approximately equal 

 size, a strongly ventricose shell, and rather numerous lateral plica- 

 tions on each side of the fold. Shells .of this type, with all the 

 variations, from Platystrophia inflata to Platystrophia prolongata, 

 occur everywhere in the Whitewater bed, in Indiana and Ohio. 

 The specimens from the upper part of the Whitewater bed. at Rich- 

 mond, Indiana, and Dayton. Ohio, are especially typical. 



Specimens belonging to the Platystrophia inflata group, but 

 with the width distinctly greater than the length, and the number 

 of lateral plications often as low as 7 to 9 on each side of the fold, 

 are common in the representatives of the Whitewater bed in Ripley, 

 Jennings, and Decatur counties, Indiana. 



Forms similar to Platystrophia inflata occur in the Liberty bed, 

 on the west side of the Cincinnati geanticline, as far south as Ray- 

 wick, Kentucky. They are associated at Cane Springs, Bardstown, 

 and elsewhere, with forms having the lateral outline of typical 

 acutilirata, but all of these Liberty forms are distinctly less ventri- 

 cose than those from the Whitewater bed near Richmond, and there 

 is a tendency toward fewer lateral plications on each side of the 

 fold. The fold frequently is more elevated, especially along the 

 middle. 



Two distinct types of shells occur in the Waynesville bed. In 

 one of these, the fold is prominent, and the lateral plications on the 



