NO. 2297. BRACHIOPOD GENOS PLATYSTROPHIA—MCEWAN. 413 



Occurrence. — Trenton group : Prosser limestone, Oshkosh, Wiscon- 

 sin; Warsaw, Fountain, and Camion Falls, Minnesota; Curdsville 

 limestone: Mercer County, Kentucky. Trenton limestone: Trenton 

 Falls, New York. 



Cotypes.—Cat. Nos. 24805, 66083, U.S.N.M. 



PLATYSTROPHIA GLOBOSA, new species. 



Plate 43, figs. 18-22. 



This is a globose species with the convexity nearly equaling the 

 width and height. The hinge line about equals the width across the 

 middle, but it may be a little less or a little greater. The lateral slopes 

 are abrupt. A slight compression of the slopes of the pedicle valve 

 produces a concavity next to the cardinal angles ; the fold is low and 

 somewhat flaring toward the front; the sinus is broad and moder- 

 ately deep, the depth being due to a slight elevation of the inner edges 

 of the lateral slopes of the pedicle valve. There are three subequal 

 plications in the sinus, four on the fold, and nine on each of the 

 lateral slopes. 



This species has the general physiognomy of Platystro-phia crassa, 

 but it has a low, spreading fold, is smaller, and has invariably eight 

 or nine plications on the lateral slopes. The plications of the fold and 

 sinus are subequal while in PlaiysiropMa crassa the lateral plications 

 of the fold and sinus are weak or have disappeared. 



Measuremenis. — 18 mm. along the hinge line, 17.7 mm. across the 

 middle, 15.8 mm. high, 15.2 mm. thick, 11.5 mm. sinal width, 5.7 

 mm. sinal depth, 2 mm. fold height. 



Occurrence. — Trenton group: Bigby limestone: Nashville, Tennes- 

 see. Trenton limestone: Ellisburg, New York. 



Coiypes.—Cfit. Nos. 66119, 66120, U.S.N.M. 



PLATYSTROPHU RHYNCHONELLIFORMIS, new species. 



Plate 42, figs. 36-38. 



This represents a small, short hinged, globose species with a moder- 

 ately elevated and compressed fold. There are three plications in 

 the sinus and four on the fold which have the pattern of the Tripli- 

 cate Group. Six and seven plications occupy the lateral slopes. The 

 slopes of the brachial valve are strongly convex in the umbonal region. 

 They descend rapidly to the cardinal and lateral and less rapidly 

 toward the frontal margin. The slopes of the pedicle valve are con- 

 vex next to the sinus and become flat or concave next to the cardinal 

 extremes. 



Measuremenis. — 7.2 mm. along the hinge line, 13 mm. wide just 

 below the middle, 10.1 mm. high, 9.4 mm. thick, 7.2 mm. sinal width, 

 4.5 mm. sinal depth, 2.8 mm. fold depth. 



Occurrence. — Trenton limestone at Ellisburg, New York. 



Cotypes.-' Cat. No. 66106, U.S.N.M. 



