Maryland Geological Survey 247 



Genus LEDA Schumacher 



Leda diversa Hall 

 Plate XXVIII, Figs. 3, 4 



Leda (Nticulana) diversa Hall, 1883, Pal. N. Y., vol. v, pt. i, plates and 



explanations, pi. xlvii, figs. 31-37. 

 Leda diversa Hall, 1885, Pal. N. Y., vol. v, pt. i, Lamellibranchiata ii, p. 329, 



pi. xlvii, figs. 31-37. 

 Leda diversa Clarke, 1903, N. Y. State Mus., Bull. 65, p. 406. 

 Leda diversa Grabau and Shimer, 1909, N. Am. Index Fossils, vol. i, p. 401, 



fig. 511c. 



Description. — "Shell small, ovate-cuneate; length about twice the 

 height; basal margin curving in the anterior portion, becoming straight 

 or nearly so, behind; posterior extremity acuminate; anterior end pro- 

 portionately large, declining rapidly from the beak and regularly 

 rounded below. Yalves gibbous in the anterior and umbonal regions, 

 attenuated behind ; beaks at about the anterior third, prominent, in- 

 curved, rising above the hinge-line; umbo prominent; umbonal ridge 

 subangular, extending from the beaks to the posterior extremity, the sur- 

 face sloping abruptly from this ridge to the hinge-line. Surface marked 

 by fine, regular, concentric striae which are merged into the umbonal 

 ridge and are obsolete on the cardinal slope." Hall, 1885. 



An exfoliated left valve, apparently of this species, was found at 

 McCoys Ferry; no evidence of the striae remains, but the form and pro- 

 portions are those of this species. 



Length, 13 mm. ; height, 5| mm. 



Occurrence. — Eomney Formation, Hamilton ]\Iember. McCoys 

 Ferr\f ; southwest of McCoys Ferry. 



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

 American Museum of Natural History. 



Leda rostellata (Conrad) 

 Plate XXVIII, Figs. 5-7 



l^ucuUtes rostellata Conrad, 1841, Geol. Surv. N. Y., An. Rep., p. 50. 

 Leda (?) rostellata Hall, 1870, Prelim. Notice Lamellibranchiata 2, p. 5. 

 Leda rostellata Hall, 1885, Pal. N. Y., vol. v, pt. i, Lamellibranchiata ii, p. 

 330, pi. xlvii, figs. 42-47. 



