Maryland Geological Survey 391 



Tropidolcptus carinatus Hall, 1857, 10th Ann. Rept. N. Y. State Cab. Nat. 



Hist, p. 151, figs. 1, 2. 

 Tropidoleptus carinatus Hall, 1859, 12th Ann. Rept. N. Y. State Cab. Nat. 



Hist, p. 31, figs. 1-4. 

 Tropidoleptus carinatus Rogers, 1858, Geo!. Penn., vol. ii, pt. ii, p. 828, fig. 



672. 

 Tropidoleptus carinatus Hall, 1867, Nat. Hist. N. Y., Pal., vol. iv, p. 407, pi. 62, 



figs. 2, 3. 

 Tropidoleptus carinatus Meek and Worthen, 1868, Geol. Survey HI., vol. iii, 



p. 427, pi. xiii, fig. 2. 

 Tropidoleptus carinatus Rathbun, 1874, Bull. Buffalo Soc. Nat. Sci., vol. i, 



p. 254, pi. ix, figs. 1, 9, 10, 26. 

 Tropidoleptus carinatus Derby, 1876, Bull. Mus. Comp. Zool., vol. iii, p. 282. 

 Tropidoleptus carinatus Rathbun, 1879, Proc. Boston Soc. Nat. Hist., vol. xx, 



p. 35. 

 Tropidoleptus carinatus Nettelroth, 1889, Kentucky Fossil Shells, Mem. Ky. 



Geol. Survey, p. 146, pi. xvii, figs. 14, 15. 

 Tropidoleptus carinatus A. Ulrich, 1892, N. Jahrb. f. Mineral., Beilageband, 



viii, p. 73, pi. iv, figs. 32-34. 

 Tropidoleptus carinatus Hall and Clarke, 1893, Nat. Hist. N. Y., Pal., vol. viii, 



pt ii, p. 304, figs. 227, 228, pi. Ixxxii, figs. 26-36. 



Description. — " Shell transversely oval ; hinge straight, not crenulated, 

 generally a little less than the greatest breadth of the shell, rounded or 

 very obtusely angular at the extremities; sides broadly rounded; basal 

 margin slightly sinuous : dorsal valve concave, having a shallow mesial 

 sinus, which is broad in front but continues above the middle of the shell 

 as a narrow groove, not larger than those between the other costs; beak 

 very small, projecting beyond tlie hinge-line, straight or citrving slightly 

 outward; dental process extended beyond the hinge-line; ventral valve 

 convex, slightly flattened and contracted toward the extremities, gibbous 

 above the center and in the umbonal region; beak obtuse and truncated 

 by the foramen ; area distinct, variable in width, extending to the cardinal 

 extremities, longitudinally striated, limited entirely to the ventral valve ; 

 foramen very broad, reaching to the beak and having a semicircular out- 

 line above, more or less closed by the prominent dental processes of the 

 opposite valve. Plications usually simple and rounded, about eighteen to 

 twenty on each valve, the middle one on the ventral valve being larger and 

 more elevated than the others, so as to form a small mesial fold or carina. 

 Surface ornamented by very fine distinct concentric striae, presenting 

 under a magnifier a very fine textile style of ornament ; substance of the 

 shell punctate throughout." Hall, 1857. 



