Bkkdk.] Carboniferous Invertebrates. 95 



DIELASMA. 



Kintj tnon Phillips), Mod. Perm. Foss. Eng. Pal. Soc, p. 46, (1850) ; etc. 



King, Proc. Dublin Univ. Zool. Rot. Asso., I, p. 260, (1859). 



Beecher and Schucbert, Biol. Soc. Wash.. VIII, pp. 71-82, (1893). 



Hall and Clarke, Pal. N. Y., VIII, pt. II, p. 293, (1893) ; etc. 



Dielasma bovidens. 



Terebratula bovidens Morton, Amer. Jour. Sci., xxix, p. 150, pi. n, f. 4, 



(1836): Meek, Fin. Rep. U. S. Geol. Surv. Neb., p. 187, pi. i, f. 7, pi. n, 



f. 4, (1872): etc. 

 Terebraiuht milltounctata Hall, Expl. Surv. R. R. Route Miss. R. to Pac. 



Ocean, in, p. 101, pi. n, ff. 1, 2, ( 1856 ) : etc. 

 Terebratula elongata Shumard < non Schloth.), Trans. St. L. Acad. Sci., 



i, p. 393, (1859). 

 Terebratula penicidosa McChesney, New Pal. Foss., p. 82, (1861); ibid., 



pi. i, f. 2, (1865). 

 Dielasma.' bovidens White, Wheeler's Expl. Surv. West 100 Mer., Prel. 



Rep., p. 21, (1874). 

 Terebratula { Dielasma) bovid<ns White, ibid., Fin. Rep., iv, p. 144, pi. 



xi, f. 10, (1875 i. 

 'Terebratula hastata Walcott (non Sowerbv), Mon. U. S. Surv., vm, p. 



224, (1893): etc. 

 Dielasma bovidens Hall and Clarke, Pal. N. Y., vni, pt. n, pp. 295, 296, 



f. 213, pi. lxxxi, ff. 29-35, (1893). 



Meek's description (in part): "Shell ovate, rounded and 

 rather compressed at the anterior and anterior lateral margins, 

 and the most convex a little behind the middle ; valves nearly 

 equally convex ; ventral valve strongly arcuate longitudinally, 

 and presenting a regularly increasing curve, from the front to 

 the beak, which is moderately prominent, and very strongly 

 and closely curved over and upon that of the other valve ; 

 foramen a little oval and not truncating the immediate apex of 

 the beak, but situated directly outside of it ; mesial sinus rather 

 wide, and rounded at the front, but narrowing and becoming 

 Less deep further back, until it dies out near the curve of the 

 umbo, which is sometimes slightly flattened. Dorsal valve 

 often nearly straight, or but slightly convex along the middle, 

 from the beak to the front, where its margin is usually some- 

 what raised for the reception of the sinus ; sides sloping from 

 the middle to the lateral margins along nearly the entire length 

 of the valve, but terminating directly under that of the other 

 valve, without any distinct curvature. Surface nearly smooth, 

 or showing moderately distinct marks of growth ; and, by the 

 aid of the magnifier, exhibiting very distinctly the moderately 



