430 FROGEEDINQS OF THE NATIONAL MUSEUM. vol. 56. 



plications occupy tlie fold which originate b}^ the bifurcation of two 

 primary plications at the beak. There are three plications in the 

 sinus; one is primary and occupies a median position, two are lateral 

 secondary plications wliicli have been implanted on the slopes of the 

 sinus. The lateral slopes are occupied b^^ five, six, or seven sharp 

 widely spaced plications. 



Measurements. — 18 mm. along the huige line, 20.5 mm. wide across 

 the middle, 13 mm. high, 12.5 mm. thick, 8.4 mm. sinal width, 

 9 mm, sinal depth, 3.6 mm. fold depth. 



Occurrence. — -Maysville group: Mount Plope and Fairmount beds 

 at Cincinnati, Ohio; Newport, Kentucky; Hays Branch, Indiana, etc. 



Plesiotypes.-^Csit. ^o. 65923, U.S,N,M, 



PLATVSTKOPHIA PROFUNDOSULCATA HOPENSIS Foerste. 



Plate 47, figs. 19-21. 



Platystrophia pro/dndosulcata hopensis Foerste, Bull. Sci. Lab. Deuison Univ., 

 vol. 16, 1910, pi. 4, fig. 4. 



This variety is more transverse, has a lower fold and shallower 

 sinus than typical specimens of the Mount Hope and Fairmount beds. 

 The}^ are more like young Platijstropliia laiicosta, but the sinus is 

 deeper. The physiognomy of the shell throughout its develpoment 

 suggests that tliis variety is the ancestor of the forms which Meek 

 took as the types of the species. 



Measurements. — -19.5 mm. along the hinge, 20.5 mm. wide across 

 the middle, 11.8 mm, high, 13 mm. thick, 10 mm. sinal width, 9 mm. 

 sinal depth, 3.3 mm. fold height. 



Occurrence. — ^Maysville group: Mount Hope beds, Cincinnati, Ohio 

 and Covington, Kentucky. 



Plesii'ty pes. —CAt. No. 65924, U.S.N.M. 



PLATYSTROPHIA CRASSA (James). 

 Plate 47, figs. 1-11. 



Orthis {Platystrophia) dentata? Meek (not Pander) Pal. Ohio, vol. 1, 1873, p. 117, 



pi. 10, fig. 8. 

 Orthis {Platystrophia) crassa Jamks, Cincinnati Quart. Journ. Sci., vol. 1, 1874, 



p. 20. 

 Orthis dentata Miller, Cincinnati Quart. Journ. Sci., vol. 2, 1875, p. 27. 

 Orthis cosfata Miller (not Pander) Cincinnati Quart. Journ. Sci., vol. 2, 1875, 



p,33. 

 Platystrophia crassa Hall and Clarke, Pal., New York, vol. 8, pt. 1, 1892, p, 



223. — Grabau and Shimer, North American Index Fossils, vol. 1, 1907, p. 258, 



figs. 308^-5.— Foerste, Bull. Sci. Lab. Denison Fniv., vol. 16, 1910, p. 59, 



pi. 4, figs. 5a-b. 

 Orthis (Platystrophia) hiforata dentata Lesley, Geol. Surv. Pennajdvania, Report 



P. 4, 1889, p. 508, figs. ^a-d. 

 Orthis centrosa Miller, North Amer. Geol. and Pal., 1889, p. 356. 



