MARYLAND GEOLOGICAL SURVEY 269 



radiating striae. Ventral valve elevated, subpyramidal, most elevated 

 at the beak, thence sloping nearly uniformly to the sides and margin; 

 area large, triangular, at right angles to the plane of the margin ; foramen 

 large, extending to the beak. Dorsal valve nearly flat, with an obscure 

 mesial sinus. 



This interesting little brachiopod is somewhat similar to several small 

 striated forms, and a restudy of the types is necessary before its true 

 generic characters can be determined. The shell from Cincinnati, Ohio, 

 figured by Hall and Clarke in 1892, is very probably of a distinct species. 



Occurrence. MARTINSBURG SHALE (Sinuites bed). Chambersburg, 

 Pennsylvania. Trenton limestone at Ottawa, Canada. 



Collection. U. S. National Museum. 



Family PORAMBONITIDAE 



Genus PARASTROPHIA Hall and Clarke 



PARASTROPHIA HEMIPLICATA Hall 



Plate XLVIII, Figs. 8-11 



Atrypa hemiplicata Hall, 1847, Pal. New York, vol. i, p. 144, pi. xxxiii, fig. x. 

 Anastrophia ? hemiplicata Winchell and Schuchert, 1893, Geol. Minnesota, 



vol. iii, p. 382, pi. xxx, fig. 29-31. 

 ParastropMa hemiplicata Hall and Clarke, 1893, Pal. New York, vol. viii, 



pt. 2, p. 221, pi. Ixiii, figs. 1-3. 

 ParastropMa hemiplicata Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, 



p. 158, pi. x, figs. 11-14. 

 ParastropMa hemiplicata Wilson, 1914, Canada Geol. Surv. Mus. Bull. No. 2, 



pp. 1-10, pi. iv, figs. 1-34. 



Description. " Shell subglobose, subpentagonal in outline, wider than 

 long, the thickness frequently equal to the length. Cardinal line short, 

 with sometimes the appearance of a small area on the pedicle valve. Each 

 valve marked by from 8 to 12 simple, subangular, radiating plications, 

 which reach from one-third to one-half the distance from the margin 

 to the beak, leaving the older portion of each valve smooth. Besides the 

 radiating plications, the entire surface is marked by fine, concentric, sub- 

 imbricating lines of growth, which are more conspicuous near the margin 



