*. 



598 Contributions to Invertebrate Palaeontology. 



MOLLUSCOIDEA. 

 BRACHIOPODA. 



Genus DISCIWA Lamarck. 



Disciiia Ifleekaiia. 



Plate XV, figs. 1-3. 



Dischm niiida? (Phil.) M. and W., Geol. 111., vol. v, p. 572, pi. 25, fig. 1. 

 Not Discina nitida Phillips, Geol. Yorkshire, vol. ii, p. 221, pi. 11, figs. 10—13. 

 Dlscina Meekana Whitf., Ann. N. Y. Acad. Sci., 1882, p. 228. 



Shell of moderate size or larger, circular or subcircular in outline. Dorsal 

 valve convex, with an elevated beak which is directed ba<rkward and situated 

 at about one-third of the length of the shell from the posterior margin. Poste- 

 rior slope slightly concave just below the apex ; anterior slope convex. Surface 

 of the shell, when preserved, marked by fine, even, but elevated and regular 

 concentric lines, with flattened interspaces ; about ten or eleven of the elevated 

 lines occiipy a space of an eighth of an inch on the middle of a shell, being 

 finer within and coarser beyond that point. On the partially exfoliated shell, 

 fine radiating vascular lines are perceptible. Ventral valve flat, discoidal, 

 circular in outline, or perceptibly elongated in some cases ; the apex a little 

 more than one-third the length of the shell from the posterior margin. Fora- 

 men small, elongate-elliptical, narrow, not extending more tlian one-fourtli of 

 the distance from the apex toward the margin, and the depression somewhat 

 further. Surface marked as in the other valve. 



This shell would appear to be identical with the one described 

 and figured by Messrs. Meek and Worthcn as D. nitida'? under the 

 supposition that it was the same as that figured by Prof. Phillips, 

 in the Geol. Yorkshire Coast, vol. ii, pi. 11, figs. 10-13; but it 

 diflers very much in outline from those figures, as well as those 

 given by other authors, in its circular form ; those being ovate, 

 narrowed behind and widened in front ; also, in having the ape.x 

 much more distant from the margin. They also cite D. Missouri- 

 ensis Shumard, as a synonym of the European species. That author 

 indicates his shell as parabolic in outline ; from which statement I 

 shQ.uld consider it as distinct from the present si)ecies. 



Formation and Locality. — In the Coal Measures at Carbon Hill 

 and Flint Ridge, Ohio; also in Illinois and Iowa. 



