NO. 2297. BRACHIOPOD GENUS PLATYSTROPHIA—McEWAN. 433 



lateral slopes is also less in Platystropliia laticosta than in Platy- 

 stropMa cypha. 



The lateral plications of the fold and sinus are weak, but they have 

 never entirely disappeared. Specimens of Platystrophia cypJia often 

 have one or both of these plications entirely missing. 



Similar specimens occur in the Waynesville beds. The latter, are 

 ventricose, more transverse and bear nine instead of seven plications 

 on the lateral slopes. 



Occurrence. — Maysville group. Leipers formation: Nashville, Ten- 

 nessee. Bellevue member: Maysville, Bullittsville, and Oldham 

 County, Kentucky; Madison, Vevay, Lawrenceburg and Manchester, 

 Indiana. Bellevue and Corryville beds: Cincinnati and elsewhere in 

 Ohio. 



Plesioty pes. ^Cnt. Nos. 48605, 50946, U.S.N.M. 



PLATYSTKOPHIA UNICOSTATA Cumings. 



Plate 48, tio's. 4-7. 



Platystrophia unicostaia Cumings, Amer. Joiu'n. Sci., ser. 4, vol. 15, 1903, pp. 

 28-29, figs. 15 a-d, p. 31.— Foerste, Bull. Sci. Lab. Denison Univ., vol. 16, 

 1910, pi. 4, fig. 6. 



Professor Cumings has described this form as a uniplicate Plaiy- 

 strophia laticosta of the Upper Maysville. It differs from that species 

 in that it is more compressed, is narrower and has a higher fold and 

 deeper sinus. 



The compression, the high fold, and deep sinus and loss of lateral 

 plications of the fold and sinus agree with PlatystropMa cyplia as do 

 also the contour of the lateral slopes. The slopes of the brachial 

 valve bend rapidly toward the cardinal margin, somewhat less 

 rapidly to the frontal margin, and with almost no bend to the lateral 

 margin. The slopes of the pedicle valve are profoundly elevated 

 along the inner margins which descend with a decided slope and form 

 a deep concavity. 



This species differs from Platystrophia cyplia in that the hinge line 

 is not more than one-fourth greater than the width across the middle 

 and the lateral plications are fewer, coarser and more widely spaced, 

 as there are only five and six. Specimens in the United States 

 National Museum labeled by James as Platystropliia cyplia belong 

 to this species. James took as his types of Platystropliia cyplia shells 

 which were conspicuously prolonged along the hinge-line and with 

 10 or 12 plications on each of the lateral slopes. 



Platystropliia unicostata is connected with Platystropliia laticosta by 

 all degrees of variants. Some individuals have three plications on 

 the sinus and four on the fold; in this case the lateral plications are 



115690— 19— Proc.N.M.vol.56 28 



