166 Systematic Paleontology — Middle Devonian 



Virginia ^ and " a cast of a ventral valve supposed to be of this species, 

 from Cumberland, Md./' was figured/ which was apparently repeated in 

 volume 8 without question regarding its specific identity." This species 

 is distinguished by its subcircular or transversely suboval outline, ventral 

 valve nearly flat or slightly concave becoming moderately convex near 

 the beak, with large muscular area in its interior, dorsal valve convex. 



Length, 27 mm. ; width, 29 mm. 



Kindle states that the specimens of the Onondaga fauna which are 

 referred to this species are somewhat smaller than the average size of the 

 species as seen in the Hamilton, seldom exceeding a length of 14 and a 

 width of 16 mm. In other features than size they correspond closely to the 

 ordinary type of this shell. 



Occurrence. — Eomney Formation, Onondaga Member. Tonoloway. 

 Hamilton Member. East bank Evitts Creek below Wolfe Mill; Williams 

 Eoad, 3/4 mile east of Queen City Hotel, Cumberland ; Williams Eoad, 14 

 mile east of Queen City Hotel, Cumberland; Ernstville. 



Co /Zeciion^.— Maryland Geological Survey; New York State Museum; 

 American Museum of Natural History. 



Rhipidomella leucosia Hall 

 Plate XIV, Figs. 1-5 



Orthis leucosia Hall, 1860, Thirteenth Rep. N. Y. State Cab. Nat. Hist., p. 80. 

 OrtMs leucosia Hall, 1SG7, Pal. N. Y., vol. iv, pp. 48, 63, pi. vii, figs. 4a-4i; pi. 



viii, figs. 9, 10. 

 Orthis leucosia Keyes, 1891, Johns Hopkins Univ. Circ, vol. xi, p. 29. 

 Rhipidomella leucosia Hall and Clarke, 1892, Pal. N. Y., vol. viii, pt. i, p. 225, 



pi. vi. fig. 16; pi. vi A, fig. 9. 

 Rhipidomella leucosia Schuchert, 1897, Bull. U. S. Geol. Surv., No. 87, p. 349. 

 Rhipidomella leucosia Clarke, 1903, N. Y. State Mus., Bull. 65, p. 298. 

 Rhipidomella leucosia Grabau and Shimer, 1909, N. Am. Index Fossils, vol. i, 



p. 265, figs. 320 d, e. 



Description. — Shell bi-oadly ovate, greatest width below the middle, 

 somewhat obtusely pointed at the beak; cardinal area short and small, 

 being less than half the width of the shell; beaks approximate. Ventral 



' Pal. N. Y., vol. iv, p. 48. 



' Ibid., pi. 6, fig. 3r. 



^ Loc. cit., pt. i, pi. vi, fig. 15. 



