>o. 22S7. BRACUIOPOD OENUS PLATYSTROPHIA—McEWAN. 427 



are six and seven plications on the lateral slopes. The surface is 

 marked by strong concentric growth lines. 



Measurements. — 13 mm. along the hinge line, 22.5 mm. wide just 

 "below the middle (this the the greatest width), 18 mm. high, 16.8 mm. 

 thick, 13.5 mm. sinal width, 10.5 mm. sinal depth, 3.3 mm. fold 

 depth. 



Occurrence. — Richmond: Elkhorn division: Elkhorn Creek, Wayne 

 County, Indiana. 



Hoioiype.^Qixi. No. 48657, U.S.N.M. 



b. PONDEROSA SUBGROUP. 

 PLATYSTROPHIA PREPONDEROSA, new species. 



Plate 4'J, figs. 6-8. 



Two Upper Trenton specimens suggest the large globose forms of 

 the genus which occur so abundantly in certain horizons of the Mays- 

 ville and Lower Richmond, to which Doctor Foerste has given the 

 the name Platysfropliia ponderosa. 



In each the fold is moderately high and compressed. It is occu- 

 pied by four subequal plications which originate by the bifurcation of 

 two primary plications at the beak.' The sinus is moderately deep. 

 It is occupied by three plications of which one is primary and occu- 

 pies a median position; two are secondary, implanted plications, and 

 occupy positions on the lateral slopes. 



The thickness nearly equals the height. The hinge line equals 

 or is somewhat less than the width across the middle. The slopes 

 of the brachial valve are convex; those of the pedicle valve are convex 

 next to the sinus and become slightly concave toward the cardinal 

 angles. They are occupied by eight and nine sharp plications. 



Measvrements. — 24 mm. along the hinge line (in one specimen the 

 hinge line equals the width across the middle), 26.7 mm. wide across 

 the middle, 20 mm. high, 20 mm. thick, 13 mm. sinal width, 12.5 mm. 

 sinal depth, 6 mm. fold depth. 



Occurrence. — Trenton group: Catheys limestone: 2 miles west of 

 Nashville, Tennessee. 



Coty pes. —Cat. No. 65871, U.S.N.M. 



PLATYSTROPHIA PONDEROSA Foerste. 



Plate 49, figs. 1-5, plate 50, figs. 4-7; plate 51, figs. 1-5, plate 52, figs. 1-3, 7-10. 



Platystrophia lynx (part) of Authors. 

 PlatystropMn biforata (part) of Authors. 



Platystrophia ponderosa Foerste, Bull. Sci. Lab., Denison Univ., vol. 14, 1909, 

 p. 225, pi. 4, fig. 14; Ohio Naturalist, vol. 12, 1912, p. 453, pi. 22, fig. 11. 



Foerste describes his species as follows: 



Platystrophia ponderosa is characterized by large size, thick valves, and quadrangular 

 outline; the brachial valve has a prominent, though rather rounded, median fold, 



