BBA.CHIOPODS. 39 



is transversely striated ;. the interior marked by numerous 

 little irregularly scattered pits, which are largest posteriorly 

 and diminish in size forward; while near the anterior margin 

 very obscure traces of minute radiating striae are sometimes 

 seen; internal scars presenting a trilobate appearance, there 

 being a short, mesial, rounded lobe nearly reaching to the 

 middle of the valve ; and nearly half way between this and 

 each posterior lateral margin there is a long, slender, diverg- 

 ing lateral lobe or impression. Dorsal valve shorter than the 

 other and subcircular in outline, its beak being apparently a 

 little truncated ; interior showing the same pitted appearance 

 seen in the other valve; visceral and muscular impressions 

 unknown. Surface of both valves marked by five concentric 

 lines. 



Horizon and localities. Cambrian shales : Mine LaMotte 

 (Madison county). 



Discina nitida (PHILLIPS). 

 Plate xxxv, fig. .6. 



Orbicula nitida Phillips, 1836: Geol. Yorkshire, vol. II, p. 221, pi. xi, figs. 



10-13. 

 Discina missouriensis Shu mard, 1858: Trans. St. Louis Acad. Sci.,vol. I, 



p. 221. 

 Discina capuliformis McChesney, 1859:- Desc. New Sp. Foss. Western 



States, p. 72. 

 Discina nitida Meek & Worthen, 1868: Geol. Sur. Illinois, vol. V, p. 572, 



pi. xxv, fig. 1. 

 Discina nitida White, 1884 : Geol. Sur. Indiana, 13th Ann. Rep., pt. ii, p. 



121, pi. xxv, fig. 9. 

 Discina nitida Keyes, 1888 : Proc. Acad. Nat. Sci. , Phih., p. 226. 



Shell small, circular in outline, low, conical, sides sloping 

 nearly straight from the apex to the margins ; apex situated 

 toward the posterior border; opposite valve flat. Surface 

 marked by concentric lines. 



Horizon and localities. Upper Carboniferous, Coal Meas- 

 ures: Clinton (Henry county), Lexington, Richmond (Ray 

 county ). 



