432 PROCEEDINGS OF THE NATIONAL MUSEUM. tol. 5G. 



PLATYSTBOPHIA CRASSA, variety. 



Plate 47, figs. 12. 



Specimens have been found in the Arnheim and Waynesville at 

 several locahtics which closely resemble FlatystrojMa crassa. The 

 only characteristic which seems to distinguish these from the Fair- 

 mount specimens is their somewhat longer hinge line. 



Measurements. — 15 mm. along the hinge, 16.8 mm. wide across the 

 middle, 15.5 mm. high, 12.6 mm. thick, 9.3 mm. sinal width, 7.2 mm. 

 sinal depth, 4 mm. fold depth. 



Occurrence. — Richmond group, Waynesville formation: Mouth of 

 Bull Creek, Clark County, Indiana; Greenwell Ford, Kentucky. 

 Arnheim: One and one-half miles south of Clark, Jefferson County, 

 Kentucky. 



Plesiotype.— Cut. No. 65953, U.S.N.M. 



PLATYSTROPHIA LATICOSTA (Meek). 



Plate 48, figs. 11-13. 



Delthyris lynx Hall, Pal. New York, vol. 1, 1847, pi. 32I>, figs. 1 0, P, Q. 

 Orthis laticostata James, Cat. Sil. Foss. Cincinnati Group, 1871, p. 10 {nomen 



nM(fc?n).— Miller, Cincinnati Quart. Jour. Sci., vol. 2, 1875, p. 27. 

 Orthis (Platystrophia) biforata var. laticosta Meek, Pal. Ohio, vol. 1, 1873, p. 116, 



pi. 10, fig. 4.— Lesley, Geol. Surv. Pennsylvania, Rep. P. 4, 1889, p. 509, figs. 



4a-d. 

 Platystrophia biforata var. laticosta Hail and Clarke, Pal. New York, vol. 8, 



pt. 1, 1892, p. 223, pi. 55, figs. 5, 8, 9 (not 6, 7). 

 Platystrophia lynx var. laticosta Cuming s and Mauck, Amer. Journ. Sci., ser. 4, 



vol. 14, 1902, p. 4.— CuMiNGS (part), Amer. Journ. Sci., ser. 4, vol. 15, 1903, 



p. 28 (footnote) p. 29, figs. e-e''\ 

 Platystrophia laticosta Cumings (part), Amer. Journ. Sci., vol. 15, 1903, pp. 30, 



122. 

 Platystrophia laticosta Foerste, Amer. Geol., vol. 31, 1903, p. 334.— Grabau and 



Shimer, N. a. Index Fossils, vol. 1, 1907, p. 258.— Foerste, Bull. Sci. Lab. 



Denison Univ., vol. 16, 1910, pi. 3, figs, la, h, 2. 



Platystrophia laticosta has a transverse shell with seven plications 

 on the lateral slopes. The fold is compressed and the sinus deep. 

 The depth of the sinus is increased by elevation of the inner edges 

 of the lateral slopes of the pedicle valve, which is the result of lateral 

 compression. 



The slopes of the brachial valve have a convex curve from the 

 front to the cardinal margin with the steepest part of the curve 

 toward the hinge. The curve from the edge of the fold to the lateral 

 margin is flatly convex. 



The chief distinction between PlatystropUa laticosta and Platy- 

 strophia cypTia is one of degree. Both have high compressed folds 

 and deep sinuses, but there is less compression of the fold and less 

 depth to the sinus in the former. The lengthwise convexity of the 



