e6 Aug. F. Foerste 



the term Platystrophia profundo-siilcata {Ohio Paleontology, vol. 

 I, plate lo, fig". 2 a-d). The length of a typical specimen is 13.5 

 mm. ; the width, 19 mm. ; the thickness through the valves, 12 mm. ; 

 the elevation of the fold above the general convexity, slightly over 

 one millimeter. 



Specimens bearing these characteristics occur in the Green- 

 dale division of the Cynthiana bed at Pleasant Valley, and at the 

 Lower Blue Lick Springs, in Nicholas county, and thence south- 

 westward to Millersburg, Paris, and Lexington; along the rail- 

 road between Colby and Winchester; between Million tunnel and 

 Valley View, all in Kentucky. 



Similar specimens occur in the Paris bed at Lexington, Frank- 

 fort, and Drennan Springs, Kentucky. A small Platystrophia 

 occurs 20 feet above the Ohio river, at Carnestown, Kentucky, 

 associated with Strophomcna vidua, in beds possibly equivalent to 

 the Paris bed. Small specimens of Platystrophia occur also along 

 the railroad l^etween Rogers Gap and Sadieville. Kentucky, in 

 strata containing Clitaiubonites rogcrsensis. 



Platystrophia colbiensis-mutata, var. nov. 



(Plate IV, figs. 3 A, B.) 



By selection, ii: is possible to differentiate from among numer- 

 ous specimens of Platystrophia colbicnsis a much smaller number 

 of individuals in which the number of plications on the fold is 

 increased to six or more plications. Usually two initial plications 

 are increased to four near the beak, and two additional plications 

 are added on the sides of the fold within a third of the length of 

 the shell from the beak, thus resulting in six plications. If any 

 additional plications are present, these are added to the exterior 

 side of the inner pair. Shells of this form are larger, broader, and 

 less convex. The fission of the plications is confined to the fold, 

 those on the sides remaining simple. Li a typical specimen 15 mm. 

 long, the width was 20 mm., the thickness through the valves 12 

 mm. The number of plications on the fold was 6, and 1 1 occurred 

 on each side. In one specimen, 9 plications are found on the fold. 



Specimens possessing these features are found at Pleasant 

 Valley, and five miles west of Winchester, Kentucky. 



In Platystrophia Ussicostata, McCoy, the fission of the plica- 

 tions occurs on the sides of the shell as well as on the fold. Platy- 



