282 SYSTEMATIC PALEONTOLOGY 



Occurrence. MARTINSBURG SHALE. (Top of the Fairview Orthor- 

 hynchula bed) just under the Oswego sandstone on Tuscarora Mountain, 

 one and one-half miles southeast of McConnellsburg, Pennsylvania. Top 

 of the Fairview or base of the McMillan formation at Cincinnati, Ohio. 

 Pulaski shales of New York and Canada. 



Collections. Maryland Geological Survey, TJ. S. National. Museum. 



Family AMBONYCHIIDAE 



Genus BYSSONYGHIA Ulrich 



BYSSONYCHIA VEEA (Ulrich) 



Plate LIV, Figs. 34-36 



Byssonychia vera Ulrich, 1893, Geol. Surv. Ohio, vol. vii, p. 629, figs. a-c. 

 Ambonychia cincinnatiensis Miller and Faber, 1894, Jour. Cincinnati Soc. 

 Nat. Hist., vol. xvii, p. 24, pi. i, figs. 8-10. 



Description. This species is quite similar to Byssonychia radiata. 

 (Hall), the type of the genus, and in fact is frequently identified with it, 

 but B. vera differs in its smaller size, finer striae (there being about 50 to 

 from 37 to 40 in the typical form of that species), shorter hinge line, 

 more evenly convex valves, and shorter byssal opening. 



Occurrence. MAETINSBURG SHALE (Eden division). Southern Penn- 

 sylvania, and in the sandstone debris of Rickard Mountain, Maryland. 

 Eden shale of the Ohio Valley. 



Collections. Maryland Geological Survey, U. S. National Museum. 



BYSSONYCHIA RADIATA (Hall) 

 Plate LVIf, Fig. 26 



Ambonychia radiata Hall, 1847, Pal. New York, vol. i, p. 292, pi. Ixxx, 



figs. 4a-l. 

 Ambonychia radiata Hall and Whitfield, 1875, Geol. Surv. Ohio, Pal., vol. ii, 



p. 79, pi. ii, fig. 2. 

 Byssonychia radiata Ulrich, 1897, Geol. Minnesota, vol. iii, pt. 2, p. 477, 



fig. 35VI. 

 Byssonychia radiata Foerste, 1914, Bull. Sci. Lab. Denison Univ., vol. xvii, 



p. 273, pi. iii, figs. 12a-c. 



Description. " Shell small to medium sized, varying in outline from 

 subquadrangular, with a rounded base, to acutely ovate, according to the 



