226 Systematic Paleontology — Middle Devonian 



conspicuous concentric ridges of the plications, the character which dis- 

 tinguishes this species from the other Buchiolas. 



Length, 7 mm. ; height, 6 mm. 



Occurrence. — Romney Formation, Hamilton Member. East bank 

 Evitts Creek below Wolfe Mill. 



Collections. — Maryland Geological Survey; American Museum of Nat- 

 ural History. 



BUCHIOLA RETROSTRIATA (von Buch)' 



Occun-en-ce.— Eomney Formation, Marcellus Member. 21st Bridge. 



Collection. — U. S. National Museum. 



[E. M. Kindle.] 



Superf^imilyNUCULACEA 

 Family NUCULIDAE 



Genus NUCULA Lamarck 

 NUCULA CORBULIFORMIS Hall 



Plate XXIII, Figs. 6-10 



Nucula corbuliformis Hall, 1870, Prelim. Notice Lamellibrancliiata 2, p. 2. 

 Nucula corbuliformis Hall, 1885, Pal. N. Y., vol. v, pt. i, Lamellibranchiata ii, 



p. 319, pi. xlvi, figs. (10, 11 ?), 24-34 (35-37 ?). 

 Nucula corbuliformis Clarke, 1903, N. Y. State Mus., Bull. 65, p. 460. 

 Nucula corbuliformis Grabau and Shimer, 1909, N. Am. Index Fossils, vol. i, 



p. 396, fig. 503f. 



Description. — " Shell of medium size, or smaller, broadly triangular, 

 subovate; length about one-fourth greater than the height; basal margin 

 broadly curving, more abiiiptly rounded at the posterior extremity; an- 

 terior end sloping rapidly from the beaks and rounded below; posterior 

 end longer and more pointed; cardinal line declining from the beaks in 

 both directions. Valves convex, gibbous in the umbonal region; beaks 

 usually at about the anterior third, sometimes subcentral, short, moder- 

 ately elevated, broad and slightly incurved; umbonal slope not distinctly 



^ For description and synonymy of this species see page 613. 



