Maryland Geological Survey r?19 



A very much distorted epeciinen was found at McCoys Ferry in Wash- 

 ington County, which is referred to the above species. The specimens 

 are so badly crushed and poorly preserved that it is not advisable to at- 

 tempt any description. 



Occurrence. — Romney Formation, Hamilton Member. McCoys 

 Ferry; southwest of McCoys Ferry; on National Road northeast of Cum- 

 berland. 



Collections. — Maryland Geological Survey ; New York State Museum ; 

 American Museum of Natural History. 



Grammtsia arouata (Conrad) 

 Plate XXII, Figs. 4-10 



Posidonia ( ?) arcuata Conrad, 1841, Geol. Surv. N. Y., An. Rep., p. 53. 

 Orammysia arcuata Hall, 1870, Prelim. Notice Lamellibranchiata 2, p. 56. 

 Grammysia arcuata Hall, 1885, Pal. N. Y., vol. v, pt. i, Lamellibranchiata ii, 



p. 373, pi. Ixi, figs. 1-9; pi. Ixiii, fig. 6 (?), pi. xciil, fig. 27. 

 Grammysia arcuata Keyes, 1891, Johns Hopkins Univ. Circ, vol. xi, p. 29. 

 Grammysia arcuata Clarke, 1903, N. Y. State Mus., Bull. 65, p. 396. 

 Grammysia arcuata Clark and Mathews, 1906, Md. Geol. Surv., vol. vi, pi. 



xvii, fig. 10. 

 Grammysia arcuata Grabau and Shimer, 1909, N. Am. Index Fossils, vol. i, 



p. 383, figs. 486e, f. 



Description. — "Shell of medium size, ovate; length about one-third 

 greater than the height; basal margin moderately curved, straight or 

 slightly concave along the middle ; posterior extremity regularly rounded ; 

 anterior end varies from regularly and narrowly rounded to obliquely trun- 

 cate below and abruptly rounded above; cardinal line nearly straight, 

 slightly declining posteriorly. Valves regularly convex below and pos- 

 teriorly, becoming gibbous above and in the umbonal region ; beaks suban- 

 terior, large and prominent, inclined forward ; umbonal ridge not defined. 

 Surface marked by fine, close concentric striae and by strong rounded or 

 subangular concentric undulations which are usually continuous from the 

 hmule to the margin of the escutcheon; these undulations are sometimes 

 duplicated, or others intercalated on the anterior half of the shell, which 

 are thence continuous to the posterior termination." Hall, 1885. 



