318 Systematic Paleontology 



with finer strias, concentric corrugations, and a more triangular ventral 

 muscle pit. Dorsal valve unknown. 



Length about 3 cm. ; width about 4 cm. 



Occurrence. — Oriskany Formation, Shriver Member. 21st Bridge, 

 North Branch near Cumberland, Maryland. 



Collections. — Maryland Geological Survey, U. S. National Museum. 



Stropheodonta (Leptostrophia) magnieica (Hall) 

 Plate LVIII, Figs. 2-5 



Strophodonta magnifica Hall, 1857, Tenth Ann. Rept. N. Y. State Cab. Nat. 



Hist., p. 54. 

 Strophodonta magnifica Hall, 1859, Nat. Hist. N. Y., Pal., vol. lii, pp. 414, 482, 



pi. xciii, fig. 4; pi. xciv, figs. 2a-2d; pi. xcv, fig. 8; pi. xcva, figs. 15-19. 

 Strophodonta vascularia Hall, 1859, ibidem, vol. iii, p. 412, pi. xcii, fig. 4; 



pi. xcv, fig. 10 (not pi. xciii, figs. 2b, 2c = ? ;S'. magniventra) , 1861. 

 Strophomena magnifi.ca Billings, 1861, Can. Jour. Sci. Arts, vol. vi, p. 348. 

 Strophomena magnifi,ca Billings, 1863, Geol. Canada, p. 961, fig. 468. 

 Strophodonta magnifica Hall, 1883, Second Ann. Rept. N. Y. State Geol., pi. 



xliv, figs. 27, 28. 

 Stropheodonta (Leptostrophia) magnifica Hall and Clarke, 1892, Nat. Hist. 



N. Y., Pal., vol. viii, pt. i, p. 288, pi. xiii, figs. 27, 28. 

 Leptostrophia magnifica Clarke, 1900, Mem. N. Y. State Mus., vol. iii, No. 3, 



p. 53, pi. vii, fig. 36. 



Description. — " Shell very large, transversely suboval, somewhat semi- 

 circular, more or less rounded at the extremities of the hinge; length and 

 breadth sometimes equal : ventral valve depressed convex in the middle 

 and umbonal regions, flattened near the lateral extremities; cardinal 

 margin sloping slightly from the beak : dorsal valve slightly concave ; 

 hinge-line crenulated, usually a little less than the width of the shell; 

 area broad, distinctly and regularly marked with transverse striae produced 

 by the prolongations of the hinge crenulations; foramen very narrow, not 

 closed. Surface marked by somewhat faint radiating striae, which bifur- 

 cate regularly about two or three times at uniform distances from the 

 beak." Hall, .1857. 



The large size, somewhat thicker shell, lower ventral cardinal area, and 

 especially the equally fine radial striae of both valves distinguish this 

 species from S. magniventra. The character pointed out by Hall for S. 



