DESCEIPTIONS OF SPECIES. ' 405 



1891. Athyris subtilUa. Whitfield, New York, Acad. Sci., Ann., vol. 5, p. 604, pi. 16, figs. 7-9. 

 Coal Measures: Hocking County, Ohio. 



1893. Seminula sublilita. Hall and Clarke, Pal. New York, vol. 8, pt. 2, p. 95, figs. 66, 67 on p. 95, 



and figs. 58, 59 on p. 86; pi. 47, figs. 17-31. (Advance distribution in fascicles.) 

 (?) Chester limestone; Caldwell County, Ky. ; Chester, 111. 

 Coal Measures: ilanhattan and Miami County, Kans.; Kansas City and Chariton County, Mo.; 



Coppers Creek, and Winterset, Iowa; Ohio. 



1894. Seminida subtiUla. Hall and Clarke, Int. Study of Brach., pt. 2, pi. 35, figs. 16-19. 

 Coal Measures: Chariton County, Mo.; Winterset, Iowa; near Kansas City, Mo. 



1895. Alhyris argerdea. Keyes, Missouri Geol. Surv., vol. 5, p. 92, pi. 39, figs, lla-d. (Date of imprint 



1894.) 

 Coal Measures: Kansas City, Lexington, and Clinton, Mo. 



1895. Seminula tubtilita. Hall and Clarke, Pal. New York, vol. 8, pt. 2, p. 95, figs. 66, 67, and 58, 59 

 on p. 86; pi. 47, figs. 17-31. 

 Coal Measures: Manhattan, Kans.; Coppers Creek, Iowa; Chariton County, Mo.; Winterset, 



Iowa; Miami County, Kans.; Kansas City, Mo.; Ohio. 

 (?) Chester limestone: Caldwell County, Ky. ; Chester, 111. 



1895. Athyris subtilUa. Whitfield, Geol. Surv. Ohio, Kept., vol. 7, p. 488, pi. 12, figs. 7-9. 

 Coal Measures: Falls Township and Webb Summit, Hocking County, Ohio. 



1896. Athyris subtilita. Smith, Am. Phil. Soc, Proc, vol. 35, p. 241. 



Upper Coal Measures: Seba-stian County, sec. 12, T. 8 N., R. 32 W., Arkansas; Poteau Moun- 

 tain, Indian Territory. 

 (?) Burlington or Lower Keokuk: Boone chert. Stone County, N. W. \ sec. 9, T. 14 N., R. 

 10 W., .Arkansas. 

 1896. Athyris subtilita. Smith, Leland Stanford Junior Univ. Publ.; Cont. Biol. Hopkins Seaside Lab.,. 

 No. 19, p. 31. 

 Upper Coal Measures: Sebastian County, Ark., sec. 12, T. 8N., R. ,32 W.; Poteau Mountain, Indian 



Territory. 

 (?) Burlington or Lower Keokuk: Boone chert, Stone County, Ark., N. W. -| see. 9, T, 14-N,, 

 R. 10 W. 

 1901). Seminula argentea. Beede, Univ. Geol. Surv. Kaasas, Kept., vol. 6, p. 105, text-fig. 3c. 



Upper and Lower Coal Measures: Marmaton Sfition, Bourbon County, lola, Kansas City, Eudora, 

 Lawrence, Lecompton, Topeka, ^Manhattan, Grand Summit, Kans. 

 19C0. Seminula argenlin. Knight, Uniw Wyoming, ^^'yoming Exp, Sta., Bull. No. 45, pi. 3, fig. 6. 



A.s .shown by our collections, this .seems to be the most universally distributed 

 species of the entire Carboniferous fauna. It has been found at over fifty stations. 

 Although many variations are to be seen in the material examined, it has not been 

 found practicable to establish lines by which specific or varietal groups shall )e 

 defined. There are some forms which have a nearly circular outline. Others ai-c 

 elongate. In some the sinus is shallow and broad; in others narrow and deep; and 

 in certain smaller types it is little more than a depressed line. . The latter, though 

 occurring alone, ma}' probably be correctly regarded as young examples of thelarg-er, 

 more strongly characterized shells. Yet all this variety of form seems to be without 



