Maryland Geological Survey 569 



Exogyra poxderosa Eoemer 



Exogyra ponderosa Roemer, 1849, Texas, p. 395. 



Exogyra ponderosa Roemer, 1852, Kreide. von Texas, p. 71, pi. ix, figs. 2a, 



2b. 

 Exogyra ponderosa Shumard, 1854, Marcy's Exploration Red River, Louisi- 

 ana, p. 178. 

 Exogyra costata (var) Conrad, 1857, U. S. and Mex. Bound. Survey, vol. i, 



pt. 2, p. 154, pi. viii, fig. 3; pi. ix, fig. 1. 

 Ostrea torosa Coquand, 1869, Mon. du Genre Ostrea, Terrain Cret., p. 38, 



pi. ix, figs. 1-3 (ex parte). 

 Exogyra ponderosa Credner, 1870, Zeitschr. deutsch. geol. Gesell., vol xxii, 



p. 229. 

 Exogyra ponderosa White, 1875, Rept. Geog. and Geol. Surveys W. 100th 



Mer., vol. iv, p. 172, pi. xiv, figs, la-lc. 

 Exogyra ponderosa White, 1884, Fourth Ann. Rept. U. S. Geol. Survey, p. 



306, pi. 1, figs. 1, 2. 

 Exogyra costata Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 39, pi. vi, 



figs. 1, 2 (ex parte). 

 Exogyra ponderosa Stanton, 1893, Bull. U. S. Geol. Survey, No. 106, p. 65, 



pi. vii, figs. 1, 2. 

 Exogyra ponderosa Hill, 1901, Twenty-first Ann. Rept. U. S. Geol. Survey, 



pt. 7, pi. xlv, fig. 1. 

 Exogyra ponderosa Hill and Vaughan, 1902, Geol. Atlas U. S. Geol. Survey, 



No. 76, illustration sheet, fig. 46. 

 Exogyra ponderosa Veatch, 1906, Prof. Paper U. S. Geol. Survey, No. 46, 



pi. ix. 

 Exogyra ponderosa Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, 



p. 458, pi. xlvii, fig. 2 ? 

 Exogvra ponderosa Stephenson, 1914, Prof. Paper, U. S. Geol. Survey, No. 



81, p. 46, pi. xiii, figs. 5-7; pi. xiv; pi. xv, figs. 1-3. 



Description. — "Testa 6" longa, 5" lata, 4" alta, grandi, crassa, ovata; 

 valva maiore inflata, gibbosa, obtuse carinata, concentrice imbricato- 

 lamellosa ; valva minore inerassata, concentrice lamellosa." — Eoemer, 

 1849. 



Type Locality. — New Braunfels, Texas. 



Description. — " Shell of adult very thick and ponderous, in outline 

 subcircular to extended subovate; dimensions of an adult individual, 

 length 111 mm., height 177 mm., convexity 94 mm.; dimensions of a 

 medium-sized specimen, length 97 mm., height 112 mm., convexity 60 mm. 

 Left or lower valve much larger than right valve, strongly convex ; attached 

 in proximity to beak to external object, this part of the shell often very 

 37 



