308 SYNOPSIS OF AMERICAN FOSSIL BRACHIOI'ODA. [bull. 87. 



Pholidops trentonensis minor Wincliell and Schu(;hert. Treutoii (Ord.). 

 Pholidops trentoiiciiHis var. minor Winchell and Scliuchert, Minnesota Geol. Sur- 



v(^y, in, 1893, p. 376, pi. 29, lig. 40. 

 Loc. St. Paul and Cannon Falls, Minnesota. 



PHOLIDOSTROPHIA Uall and Clarke, (lenotype Stropliodouta nacrea 



Hall=Choiietes('?) ioweusis Owen. 



Pholidostrophia Hall and Clarke, Pal. New York, VIII, Pt. I, 1892, p. 287;— 

 Eleventh Ann. Rep. N. Y. State Geologist, 1894, j). 281. 



Pholidostrophia iowaensis (Owen). Oorniferous and Hamilton (Dev.). 



Cliouctes (f) iowonsis Owen, Geol. Survey Wisconsin, Iowa, Minnesota, 1852, p. 



584, pi. 3A, lig. 7. [See specimens in U. S. Nat. Mas., Cat. Invert. Foss., 



17942.] 

 Chonetes sp. iindet. Owen, Ibidem, 1852, pi. 3A, iig. 17. [See specimens in U. S. 



Nat. Mas., Cat. Invert. Foss., 17916.] 

 Strophomena (Strophodonta) nacrea Hall, Tenth Rep. N. Y. State Cab. Nat. Hist., 



1857, p. 144. 

 Strophomena lepida Hall, Geol. Iowa, I, 1858, p. 493, pi. 3, tig. 3. — Billings, 



Canadian Jour. Sci. Arts, VI, 1861, p. 344. 

 Strophodonta nacrea Hall, Pal. New York, IV, 1867, p. 104, pi. 18, lig. 1 : — Second 



Ann. Rep. N. Y. State Geol., 1883, pi. 46, figs. 20-24.— Nettelrotl^, Kentucky 



Fossil Shells, Mem. Kentucky Geol. Survey, 1889, p. 146. 

 Stropheodonta (Pholidostrophia) nacrea Hall and Clarke, Pal. New York, VIII, 



Pt. I, 1892, p. 287, pi. 15, figs. 20-24; Pt. II, 1895, pi. 84, tig. 11. 

 Loc. Iowa City, Iowa; western New York; Columbus, Ohio; Falls of Ohio ; Rock 



Island, Illinois; Alpena, Michigan; Ontario, Canada. 

 Oba. Owen's type specimens preserved in the United States National Museum 



prove to be identical with Strophomena lepida, which Hall in 1867 said is a 



synonym for Stropheodonta nacrea. 



Plsesiomys Hall and Clarke=Dinorthis. 



PLATYSTROPHIA King. Genotype Terebratulites biforata Schlotheim. 



Platystrophia King, Mou. Permian Fossils of England, Pal. Soc, 1850, p. 116. — 

 Hall, Geol. Soc. America, 1, 1889, pp. 19, 20.— Hall and Clarke, Pal. New York, 

 VIII, Pt. I, 1892, p. 200.— Winchell and Schuchert, Minnesota Geol. Survey, 

 III, 1893, p. 454. — Hall and Clarke, Eleventh Ann. Rep. N. Y. State Geologist, 

 1894, p. 268. 



Obs. It is doubtful whether all the various forms of Platystrophia can be regarded 

 as species. This genus is nearly always abundantly represented by one or 

 more forms throughout the American Ordovician and Silurian systems. 

 When individuals of the same region or of widely .separated localities are 

 compared with each other it is apparent that the specitic characters arc 

 very inconstant. Individuals of a stratum, however, are fairly constant in 

 form, size, and plications, and it is this limited constancy that has served in 

 many of the following species. 



Platystrophia acuminata James. Lorraine (Ord.), 



Orthis (Platystrophia) acuminata James, The Palaiontologist, 1, 1878, p. 7. 

 Loc. Cincinnati, Ohio. 



Platystrophia acutilirata (Oonrad). Lorraine (Ord.). 



Delthyris acutilirata Conrad, Jour. Acad. Nat. Sci. Philadelphia, VIII, 1842, p. 



260, pi. 14, fig. 15. 

 Orthis (Platystrophia) acutilirata Meek, Pal. Ohio, I, 1873, p. 119, pi. 10, tig. 5. 

 Orthis acutilirata Miller, Cincinnati Quart. Jour. Sci., II, 1875, p. 28. 



