424 CARBONIFEROUS FORMATIONS AND FAUNAS OF COLORADO. 



at Beaumont, Butler County, Kans. A single specimen from the Leadville region 

 also has Ijocn referred here. It can not be identified witli c(>rtainty. I)ut seems to he 

 nearest to M. wyomingenais. 



Locality and hm'izcm. — San Juan region (stations 2340, 2341, 2342, 2345, 2349); 

 Rico formation. Leadville district (station 2257); base of the Weber formation. 



Myalina subquadrata Shumard? 



PI. VIII, figs. 6, 7. 



1855. Mijalum xnhquadrala. Shumard, Missouri Geol. Surv., p. 207, PI. C, fig. 17. 



Upper Coal Measures: On Missouri River, 2 miles below the mouth of the Little Nemaha. 

 186-1. Myalina Kuhquadrata. Meek and Hayden (pars), Smithsonian Cont. Knowledge, vol. 14, No. 

 172, p. 32. 

 Coal Measures: Leavenworth City, Kans. 

 1866. Myal'ma Kiibqnadrata. Geinitz, Carb. und Dyas in Nebraska, p. 27, tab. 3, figs. 25, 26. 



Upper Coal Measures: Nebraska City, Nebr. 

 1872. Myalina subquadrata. Meek, U. S. Geol. Surv. Nebraska, p. 202, pi. 4, fig. 12; pi. 9, fig. 6. 



Upper Coal Measures: Nebraska City, Bennetts Mill, and Bellevue, Nebr. 

 1884. Myalina subquadrata. White, Geol. Surv. Indiana, 13th Rept., p. 140, pi. 29, figs. 1, 2; pi. 30, 

 figs. 1, 2. 

 Upper Coal Measures: Knox, Gibson, and Posey counties, Ind. 

 1886. Myalina subquadrata. Heilprin, 2d Geol. Surv. Pennsylvania, Ann. Rept. for 1885, p. 456; 

 p. 446, fig. 15; p. 454, fig. 15a. 

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

 1886. Myalina subquadrata. Heilprin, Proc. and Coll. Wyoming Hist, and Geol. Soc, vol. 2, pt. 2, 

 p. 273, fig. 15a; p. 274, fig. 15. 

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

 1895. Myalina subquadrata. Keyes, Missouri Geol. Surv., vol. 5, p. 118, pi. 44, figs, la, b, 2a, b. 

 (Date of imprint, 1894.) 

 Upper Coal Measures: Kansas City, Mo. 

 1900. Myalina subquadrata. Beede, Univ. Geol. Surv. Kansas, Rept., vol. 6, p. 138, pi. 16, figs. 10, 10b. 



Carboniferous: Kansas City, Melvern (Osage County), Topeka, Lawrence, Kans. 

 1900. Myalina subquadrata. Knight, Univ. Wyoming, Wyoming Exp. Sta., Bull. No. 45, pi. 3, fig. 1. 



This well-known and widely distributed species is represented in several of the 

 collections examined, and by a number of specimens. In the Rico formation of the 

 San Juan region it is abundant and attains a large size, especially on the Dolores 

 River (station 2343) and on Scotch (]reek (station 2340). I have identified it also in 

 the Hermosa formation of the same region, in Big Percent Creek (station 2200), and 

 on the west side of the Animas Valle}' (station 2205). In the Hermosa formation, 

 however, it is represented by a few small shells, fragmentary and poorl}' preserved. 

 Associated with the larger specimens at station 2205 an isolated left valve was found 

 having a smaller size and a more oblique shape. The length along the hinge line is 

 only 13 mm. and the axis is inclined to the hinge at an angle of about 45°. The gen- 



