Bkede.] Carboniferous Invertebrates, 55 



ORBICULOIDEA. 



d'Orbipuv, Prodrome de Pal. Strat.. I, p. 44, (1850). 

 Dall, Bull. Bins. Comp. Zool., Ill, p. 37, (1871); etc. 



Orbiculoidea missouriensis. Plate VIII, figs. 1-lc. 



Discina missouriensis Shumard, Trans. St. L. Acad. Sci., i, p. 221, (1858). 

 Discina /n't/do? Meek and Worthen ( non Phillips), Geol. Surv. 111., v, 



p. 572, pi. xxv, f. 1, (1873): White, 13th Ann. Rep. St. Geol. Ind., p. 121, 



pl. xxv, f. 10, (1884); etc. 

 Discina meekiana Whitfield, Ann. N.Y. Acad. Sci., n, p. 288, (1882); etc. 

 Orbiculoidea missouriensis Schuchert, Bull. 87, U.S. Geol. Surv., p. 281, 



(1897i. 



White's description (in part) : u Shell small, subcircular, de- 

 pressed conical, the sides sloping nearly straight from the apex 

 to the margin ; apex prominent, situated about one-third the 

 diameter of the shell from the posterior border ; lower valve flat 

 with the usual depression around the foramen ; surface of both 

 valves marked by concentric lines and fine lamellations. Di- 

 ameter of an average example about 8 mm." 



In this shell the height of the apex is about one-third the di- 

 ameter of the shell. The concentric lines are prominent in 

 well-preserved specimens and are sharply elevated, separated 

 by wider, shallow furrows. The sulcus extends two-thirds or 

 all the distance to the posterior margin. The inner lamina 1 of 

 the dorsal valve show a radiate structure. 



Range and distribution : Upper and Lower Coal Measures ; 

 Fort Scott ; Rosedale, Wyandotte county ; Lansing, Leaven- 

 worth county ; Topeka. 



Orbiculoidea convexa. Plate VIII. figs. 3, 3b. 



Discina convexa Shumard. Trans. St. L. Acad. Sci., i, p. 221,(1858); 



White, 13th Ann. Rep. St. Geol. Ind., p. 121, pl. xxv, f. 9, (1884); etc. 

 <)rh;<-nh,i<h a eo,ny xa Schuchert, Bull. 87, U. S. Geol. Surv., p. 278, (1897 }. 



White's description: "Upper valve broadly but somewhat 

 prominently convex ; subcircular in marginal outline ; the 

 height nearly equal to one-half the diameter ; apex somewhat 

 obtuse, but moderately prominent, situated about one-third the 

 diameter of the shell from its posterior margin ; surface marked 

 by the usual distinct lines of growth. A small under valve was 

 found in the same locality as the upper valve above described, 

 and probably belongs to this species. It shows a similar sur- 



