DESCRIPTIONS OF SPECIES. 297 



1877. Athyris mbquadrataf Hall and Whitfield, U. S. Geol. Expl. 40th Par., Rept., vol. 4, p. 271, pi. 

 5, figs. 19, 20. 

 Wasatch limestone: Snowstorm Hill, near Dry Canyon, Oquirrh Mountains, Utah. 

 1886. Athyris subquadrata. Heilprin, 2d Geol. Surv. Pennsylvania, Ann. Rept. for 1885, p. 453, p. 440, 

 fig. 2. 

 Mill Creek limestone. Upper Coal Measures: Wilkesbarre, Pa. 

 1886. Athyris guhqvadrata. Heilprin, Proc. and Coll. Wyoming Hist, and Geol. Soc, vol. 2, pt. 2, 

 p. 269, fig. 2. 

 Mill Creek limestone. Upper Coal Measures: Wilkesbarre, Pa. 

 1891. Athyris subquadrata. Whitfield, New York Acad. Nat. Sci., Ann., vol. 5, p. 585, pi. 14, figs. 1-3. 

 Maxville limestone: Newtonville and Maxville, Ohio. 



1893. Seminula subquadrata. Hall and Clarke, Pal. New York, vol. 8, pt. 2, p. 95, pi. 47, figs. 7-9, 15, 



16; pi. 84, figs. 30, 31. (Advance distribution in fascicles.) 

 Chester lime.stone: Crittenden County, Ky. 

 St. Louis limestone: Spergen Hill, Ind.; Pella, Iowa. 

 Kaskaskia limestone: Chester, 111. 



1894. Seminula .subquadrata. Hall and Clarke, Int. Study of Brach., pt. 2, pi. 35, figs. 13, 15. 

 Chester limestone: Crittenden County, Ky. 



St. Louis limestone: Pella, Iowa. 



1895. Athyris subquadrata. Keyes, Missouri Geol. Surv., vol. 5, p. 92. (Date of imprint, 1894.) 

 Kaskaskia limestone: St. Mary, Mo. 



1895. Seminula subquadrata. Hall and Clarke, Pal. New York, vol. 8, pt. 2, p. 95, pi. 47, figs. 7-9, 15, 

 16; pi. S4, figs. 30, 31. 

 Kaskaskia limestone: Che.ster, 111.; Crittenden Coimty, Ky. 

 St. Louis limestone: Pella, Iowa; Spergen Hill, Ind. 

 1895. Athyris subquudratd. Whitfield, Geol. Surv. Ohio, Rept., vol. 7, p. 472, pi. 10, figs. 1-3. 



Maxville limestone: Newtonville and Maxville, Ohio. 

 1897. Athyris subquadrata. Weller, New York Acad. Sci., Trans., \ol. 16, p. 258, pi. 18, fig. 16. 

 (Date of volume, 1898.) 

 Batesville sandstone: Batesville, Ark. 



Near the top of the Blue limestone, at several localities in the Leadville region, 

 a species of Seminida occurs in some abundance (especially at station 2375). None of 

 the fossils of this formation are well preserved or in a condition favorable for study, 

 and the seminulas have suli'ered equally with the rest. Suspending for the moment 

 the discu.ssion of the generic position of this form, it will be desirable to comment 

 upon its specific characters and its relation to the species to which I have referred it. 



My specimens show considerable variety in size, the largest observed having a 

 length of probably 20 mm., the others ranging to half that or less. These inequalities 

 in size evidently correspond to differences in age. The shape is subquadrate to' 

 subcircular, the width being about the same as the length, or usually a trifle greater. 

 The upper portion of the contour is made by approximate right lines, extending 

 perhaps halfway down the figure. The inferior outline is either regularlj' curved or 

 subrectilinear, depending somewhat on the degree of development of the fold and sinus. 

 The feature last mentioned is faint, but can usually be ascertained. It is apt to be 



