NO. 229T. BRACHIOPOD GENUS PLATYSTROPHIA—McEWAN. 407 



Occurrence. — Niagara group: Laurel limestone, St. Paul and 

 Heatons Branch, East of St. Omar, Indiana. 

 Cotypes.— Cat. No. 66116, U.S.N.M. 



b. STJBGROTTP B— TRENTON SPECIES. 

 PLATYSTROPHIA TRENTONENSIS, new species. ' 



Plate 42, figs. 3-6. 

 Platystrophia hiforata Grabau and Shimer, North American Index Fossils, vol. 

 1, 1903, p. 258.— CuMiNGS (part), Amer. Joum. Sci., ser. 4, vol. 15, 1903, p. 41. 



In the Trenton limestone occurs a long hinged form which has 

 the plication pattern of the Biplicate group. The hinge line is 

 equal to or greater than the width across the middle. The fold is 

 scarcely elevated above the convexity of the brachial valve, and it 

 bears four plications of equal strength. The sinus of the pedicle 

 valve is moderately deep and bears three plications of equal 

 strength. There are twelve to fifteen plications on the lateral 

 slopes. 



This species has some resemblance to Platystrophia amoena longi- 

 cardinalis, new variety, but the latter species belongs to the tripli- 

 cate group. 



Measurements. — 16.7 mm. along the hinge line, 16 mm. across the 

 middle, 12.3 mm. high, 11 mm. thick, 7.4 mm. sinal width, 4.7 mm. 

 sinal depth, 0.7 mm. fold height. 



Occurrence. — Trenton group. Prosser limestone at Fountain and 

 Montorville, Minnesota, and at Decorah, Iowa. Cm-dsville lime- 

 stone at Troy, Kentucky. Trenton limestone at St. Joseph Island, 

 Lake Hm-on. 



Coty pes. —Ca,t. Nos. 39052, 66097, U.S.N.M. 



PLATYSTROPHIA TRENTONENSIS CHAMPLAINENSIS, new Tsrietjr. 



Plate 42, figs. 9-11. 

 Platystrophia hiforata Cumings (part), Amer. Jonrn. Sci., ser. 4, vol. 15, 1903, 

 p. 41. 



In the Trenton limestone of Lake Champlain is a small form which re- 

 sembles Platystrophia elegantula, new species in the shape of the shell 

 but the forms are easily distinguished by their plication patterns. 



This variety differs from typical specimens of the species in pos- 

 sessing a much shorter hinge-line and in a tendency toward obsoles- 

 cence of plications next to the cardinal angles. 



Occurrence. — Trenton limestone, near Lake Champlain, New York. 



Hohtype.—Csit. No. 66099, U.S.N.M. 



PLATYSTROPHIA TRENTONENSIS PERPLANA, new variety. 



Plate 42, figs. 12-14. 

 Platystrophia hiforata Weller, Pal. New Jersey, vol. 3, 1903. p. 153, pi. 9, figs. 

 25-28. 



This variety is distinguished from other members of the species 

 by its greater width and height and thinner form. The fold is 



