366 SYSTEMATIC PALEONTOLOGY 



Genus LEPERDITELLA Ulrich 



LEPERDITELLA TUMIDA (Ulrich) 



Plate XLIII, Figs. 10-12 



Leperditia tumida Ulrich, 1892, Amer. Geol., vol. x, p. 264, pi. ix, figs. 1-3. 

 Leperditella tumida Ulrich, 1894, Geol. Minnesota, vol. iii, pt. 2, p. 636. 



Description. Valves ovate, leperditoid, with a straight back, rather 

 short, with the posterior end widest, tumid, the convexity of the surface, 

 except for a slight flattening and lengthening of the dorsal and anterior 

 slopes, nearly uniform. Surface obscurely punctate, otherwise smooth, 

 there being no external signs of either the eye-tubercle or muscle spot. 

 Right valve a little smaller than the left and fitting into a groove in it. 



Length of a large right valve, 2.6 mm. ; height, 1.82 mm. ; thickness, 

 0.75 mm. 



This is one of the characteristic microscopic fossils of the Lowville 

 limestone in the Ohio and Appalachian valleys. 



Occurrence. CHAMBEKSBURG LIMESTONE (Tetradium cellulosum 

 bed). Fort London and other localities in Franklin County, Pennsyl- 

 vania. 



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



Genus APARCHITES Jones 



APAKCHITES MINUTISSIMUS (Hall) 



Plate LV, Fig. 33 



Leperditia (Isochilina') minutissima Hall, 1872, 24th Rep. New York State 

 Cab. Nat. Hist, p. 231, pi. viii, fig. 13 (advance sheets, 1871, p. 7). 



Leperditia (Isochilina) minutissima Hall and Whitfield, 1875, Geol. Surv. 

 Ohio, Pal., vol. ii, p. 102, pi. iv, fig. 4. 



Aparchites minutissimus Ulrich, 1889, Geol. Surv. Canada, Cont. Micro.-Pal., 

 pt. 2, p. 49, pi. ix, fig. 5. 



Description. " Carapace minute, less than two-hundredths of an inch 

 in length, the width being about two-thirds the length, greatest at the 

 anterior third, giving a broadly ovate outline, with a straight cardinal 

 margin of about two-thirds the length of the valve. 



