Cincinnatian and Lexington Fossils 6y 



In general outline, in the ventricose appearance of the body of 

 the shell, and in the number of plications, however, Conrad's figure 

 resembles the common Whitewater form from the vicinity of Rich- 

 mond, Indiana, and from corresponding horizons in Ohio and else- 

 where in Indiana, rather than the Liberty or Arnheim forms seen 

 within a reasonable radius of Louisville, Kentucky. His type 

 specimen evidently was mislabelled as far as the localitv was con- 

 cerned. Conrad described other species from Richmond. Indiana. 

 This identification of Platystrophia acufilirafa with the Whitewater 

 form is in common use, and nothing can be gained by seeking some 

 Kentucky source for the origin of Conrad's type, especiallv in view 

 of the absence of the type specimen itself. 



As in the case of Platystrophia cypha, there is everv variation 

 between specimens in which the length of the hinge-line does not 

 exceed the width of the shell across the middle, or even is a little 

 less, and those in which the shell is prolonged into spine-like pro- 

 jections along the hinge-line. 



The first mentioned extreme forms the variety inHata of James. 

 Specimens of this type (plate iv, fig. 8 A,B) are strongly gibbous. 

 The hinge-line about equals the width of the shell, and the latter is 

 not more than one-fifth greater than the length in specimens which 

 are considered most typical of this variety. One of the type speci- 

 mens preserved in the James collection in the \Valker Museum of 

 Chicago L'niversity, belonging to a series labelled Platystrophia 

 inflata and numbered 1561, has the following dimensions: length, 

 17.5 mm.; width across the middle of the shell, 2t^ mm.; length of 

 the hinge-line, 23.5 mm.; gibbosity of the shell, 21 mm. The 

 characteristic low, broad, rounded fold and shallow sinus of 

 Platystrophia acutilirata are present. 



The other extreme (plate iii. figs. 8 A,B). called Platystrophia 

 prolougata bv James, consists of shells distinctly prolonged along 

 the hinge-line into spine-like projections. Frequently these pro- 

 jections are merelv distinctly acute, with a slightly concave outline 

 on the lateral side of the shell, and scarcely can be called spine-like. 

 Specimens of the latter type form the typical Platystrophia acutili- 

 rata of Conrad, as here identified and as figured by Meek in the 

 Ohio Paleontology, vol. i, plate x, fig. 5a. 



Platystrophia acutilirata-sciicx, the gerontic characteristics of 

 which are so admirably described by Cumings, includes two forms. 

 The one first figured {Indiana Geol. Survey, 32nd Report. 1908. 



