560 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



EUMETRIA Hall, 1864. 



EUMETRIA VERNEUILIANA Hall. 



PI. LXVIII, figs. 12a., 12b. 



Betzia verneuilana Hall, 1858: Geol. Surv. Iowa, Vol. I, Pt. II, p. 657, PI. XXIII, 



figs. la-Id. Hall, 1858: Trans. Albany lust, Vol. IV, p. 9. 

 Betzia vera Hall, 1S58: Geol. Surv. Iowa, Vol. I, Pt. II, p. 704, PL XXVII, figs. 3a-3c. 



Hall, 1863: Sixteenth Kept. New York State Cab. Nat. Hist., p. 55, figs. 1-3, 



p. 59. 

 Betzia verneuili Hall, 1803: Ibid., p. 55, fig. 2. 

 Eumetria verneuilana Whitfield, 1882: Bull. Am. Mus. Nat. Hist., Vol. I, p. 50, PL 



VI, figs. 28-30. 

 Eumetria verneuiliana Hall, 18S3: Twelfth Kept State Geologist, Indiana, p. 335, PL 



XXIX, figs. 28-30. 

 Betzia radialis Walcott, 1884: Mon. U. S. Geol. Surv., Vol. VIII, p. 220, PL VII, figs. 



5, 5« (5b1). 

 Eumetria verneuiliana and vera Hall and Clarke, 1893: Pal. New York, Vol. VIII, Pt. 



II, p. 117, figs. 104, 105; PL LI, figs. 13-26, 34-37; PI. LXXXIII, figs. 26, 27. 



In the Mississippi Valley Eumetria verneuiliana is confined to the St. 

 Louis and Chester divisions of the Lower Carboniferous series. It includes 

 a number of shells varying extremely in size, proportion, and surface sculp- 

 ture, but which it has not. yet been possible to subdivide and establish as 

 independent specific types. 



The same type of shell, however, appears much earlier in the Lower 

 Carboniferous; for in the Kinderhook division we find Eumetria altirostris 

 White, 1 Hustedia triangularis Miller, 2 Acambona osagensis Swallow, 3 Betzia f 

 circularis Miller, 4 Betzia? plicata Miller, 5 and Betzia popeana Swallow, 6 all 

 externally similar and more or less closely related forms. 



The genus Acambona includes mostl} T species from Lower Carbonifer- 

 ous horizons, but the internal structure of the genus is imperfectly known, 

 and externally it is inseparable from Eumetria, even Eumetria verneuiliana. 



E. verneuiliana, as it occurs in the Madison limestone, does not, attain 

 the size often seen in specimens from the Mississippi Valley. It is, on the 



1 1862. Proc. Boston Soc. Nat. Hist., Vol. IX, p. 28. 



-1894. Eighteenth Ann. Rept. Geol. Surv. Indiana, p. 315, PI. IX, ligs. 25, 26. 



■I860. Trans. St. Louis Acad. Sci., Vol. I, p. 653. 



■'1894. Eighteenth Ann. Kept. Geol. Surv. Indiana, p. 316, PI. IX, tigs. 32-34. 



■1894. Ibidem, p. 316, PI. IX, figs. 29-31. 



6 1S60. Trans. St. Louis Acad. Sci., Vol. I, p. 654. 



