248 Systematic Paleontology — Middle Devonian 



Leda rostellata Clarke, 1903, N. Y. State Mus., BulL 65, p. 407. 

 Leda rostellata Grabau and Shimer, 1909, N. Am. Index Fossils, vol. 1, p. 401, 

 flg. 511d. 



Description. — " Shell small, falciform ; length more than twice the 

 height; basal margin gently curving from the posterior extremity, more 

 rapidly curving anteriorly ; posterior end attenuate, arching upward, with 

 the extremity narrowly rounded or subtruncate; anterior end compara- 

 tively short, abruptly rounded; cardinal line oblique, declining pos- 

 teriorly, and regularly curved. Valves convex, somewhat gibbous in 

 the umbonal region, depressed-convex posteriorly; beaks between the an- 

 terior third and fourth of the length of the shell; iimbonal ridge dis- 

 tinctly defined, sharply angular above. Surface marked by fine, regular, 

 equal, sharp concentric striae, which converge upon the posterior end of 

 the shell, cross the umbonal angle, and are obsolescent on the post-car- 

 dinal slope; hinge crenulated with minute teeth which extend half the 

 distance from the beak to the posterior end." Hall, 1885. 



On the ^^ational Eoad west of Tonoloway Ridge a broken right valve 

 of what is considered a young specimen of this species was found. 

 Although the posterior end is wanting, still it apparently is of falciform 

 shape and the surface is marked by very fine, sharp concentric striae, 

 which are finer and more regular than those of L. diversa. Later, addi- 

 tional specimens were found at other localities. 



Occurrence. — Romney For:mation, Hamilton Member. B. & 0. 

 R. R. cut at 21st Bridge; in Jennings Run % mile west of Corriganville 

 ( ?) ; on Xatioual Road 1/2 ™il6 west of Tonoloway Ridge. 



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



Superfamily ARCACEA 

 Family PARALLELODONTIDAE 



Genus PARALLELODON Meek 



Parallelodon hamiltoniae (Hall) 



Plate XXVIII, Figs. 8-12 



Macrodon liamiltoniae Hall, 1870, Prelim. Notice Lamellibranchiata 2, p. 13. 

 Macrodon hamiltoniae Hall, 1885, Pal. N. Y., vol. v, pt. i, Lamellibranchiata 

 ii, p. 349, pi. 11, figs. 1-7, 9, 10. 



