192 Systematic Paleontology — Middle Devonian 



cut at Hancock Station, W. Va. ; on the Komney-Hanging Rock Road 

 about ^ mile north of Romney, W. Va. 



Collections.— Ma.ry\an6. Geological Survey; New York State Museum; 

 American Museum of Natural History. 



Spirifer AUDACULus (Conrad) 

 Plate XVITI, Pigs. 7-9 



Delthyris audacula Conrad, 1842, Jour. Acad. Nat. Sci. Phila., vol. viii, p. 202. 

 Delthyris medialis Hall, 1843, Geol. N. Y., pt. iv, p. 208, fig. 8. 

 Spirifer medialis Hall, 18.^7, Tenth Rep. N. Y. State Cab. Nat. Hist., p. 157. 

 Delthyris viedialis Rogers, 1858, Geol. Penna., vol. ii, pt. ii, p. 828, fig. 669. 

 Spirifera medialis Hall, 1867, Pal. N. Y., vol. iv, p. 227, pi. xxxviii, figs. 1-25. 

 Spirifera audacula Whitfield, 1SS2, Geol. Wisconsin, vol. iv, p. 329, pi. xxv, 



figs. 25, 26. 

 Spirifera medialis Keyes, 1891, Johns Hopkins Univ. Circ, vol. xi, p. 29. 

 Spirifer audaculus Hall and Clarke, 1893, Pal. N. Y., vol. viii, pt. ii, pp. 29-31, 



39, pi. xxiv, figs. 1-13; pi. xxix, fig. 5. 

 Spirifer audaculus Scliuchert, 1897, Bull. U. S. Geol. Surv., No. 87, p. 382. 

 Spirifer audaculus Clarke, 1903, N. Y. State Mus., Bull. 65, p. 309. 

 Spirifer audaculus Grabau and Shimer, 1909, N. Am. Index Fossils, vol. i, 



p. 329, fig. 420a. 



Description. — Shell medium size; valves moderately convex in young 

 specimens, becoming ventricose in old shells; hinge-line generally ex- 

 tended beyond the width of the shell below. Ventral valve usually more 

 convex than the dorsal; incurved beak; cardinal area commonly of more 

 than medium height; longitudinally striated and divided in the middle 

 by the delthyrium which is about twice as high as wide ; mesial sinus 

 well defined, extending to the apex, of moderate width, rather deep and 

 generally rounded at the bottom. Dorsal valve moderately convex; beak 

 small and slightly incurved ; cardinal area linear ; mesial fold prominent, 

 rising abruptly at the sides and rounded or slightly flattened on top; 

 cardinal angles slightly reflected. Surface marked by twenty or more 

 simple plications on each side of the fold and sinus and the principal 

 ones, especially of the ventral valve, are often marked along the center 

 by a threadlike groove; toward the front are numerous, often imbricat- 

 ing, concentric lines. 



