248 SYSTEMATIC PALEONTOLOGY 



of the Chazyan. In east Tennessee it is found in the supposedly equiva- 

 lent horizon the Lenoir limestone. 



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



DINOETHIS PECTINELLA (Emmons) 

 Plate XLV, Figs. 8, 9 



Orthis pectinella Emmons, 1842, Geol. New York, Rep. 2d Dist, p. 394, fig. 2. 



Dinorthis pectinella Hall and Clarke, 1892, Pal. New York, vol. viii, pt. 1, 

 pp. 195, 222, 228, pi. v, figs. 27-33. 



Orthis (Dinorthis) pectinella Winchell and Schuchert, 1893, Geol. Minne- 

 sota, vol. iii, p. 424, pi. xxxii, figs. 31-34. 



Dinorthis pectinella Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, 

 p. 154, pi. ix, figs. 29, 30. 



Description. " Shell resupinate, transversely subelliptical in outline, 

 wider than long, in about the proportion of four to three; cardinal line is 

 usually less than the greatest width of the shell, the cardinal extremities 

 rounded; surface of each valve marked by from 22 to 30 prominent, 

 rounded, simple costae, which are equal in width to the spaces between, 

 and are crossed by fine, closely crowded elevated, concentric lines of 

 growth. Pedicle valve slightly convex near the beak, flattened on the 

 sides, with a broad, shallow, ill-defined depression along the center, 

 usually most distinct in front, but frequently nearly obsolete. Cardinal 

 area moderately large and well defined, flat, lying nearly at right angles 

 to the plane of the shell. Brachial valve regularly convex, most prominent 

 in the center, flattened and slightly deflected near the cardinal extremi- 

 ties. Cardinal area much narrower than that of the opposite valve, lying 

 nearly in the plane of the shell. 



" The dimensions of the nearly perfect pedicle valve are : Length, 

 21 mm.; width, 27.5 mm." Weller, 1903. 



Occurrence. CHAMBERSBUEG LIMESTONE (Echinospherites bed). 

 Wilson and Pinesburg, Maryland. 



This species occurs in the Upper Black River and Early Trenton of 

 New York and Canada, and the Ohio and Mississippi valleys. 



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



