MARYLAND GEOLOGICAL SURVEY 261 



Genus RAFINESQUINA Hall and Clarke 



RAFINESQUINA CHAMPLAINENSIS Raymond 



Plate XLI, Figs. 8, 9 



Rafinesquina champlainehsis Raymond, 1902, Bull. Amer. Pal., vol. iii, p. 37, 



pi. xviii, figs. 5, 6. 

 Rafinesquina champlainensis Raymond, 1911, Ann. Carnegie Mus., vol. vii, 



p. 233, figs. 6-9. 



Description. " Shell large, ventricose, almost hemispheric. Length 

 and width nearly equal. Hinge line usually a little longer than the width 

 below, and the cardinal extremities are produced into broad, rounded 

 ears. The pedicle valve is strongly and evenly convex, the highest point 

 being about the middle of the valve. The brachial valve is flat on the 

 umbo and concave in front, following the curvature of the opposite 

 valve. Cardinal area on the pedicle valve rather wide. . Delthyrium 

 covered by a broad convex deltidium. Area of brachial valve linear. 

 The surface is marked by very numerous fine radiating striae, every 

 third or fourth one of which is stronger than the ones between. The 

 striae increase by implantation. In the partially exfoliated state in 

 which the specimens are usually found, the striae appear nearly equal 

 and the shell structure fibrous." Raymond, 1902. 



Occurrence. CHAMBERSBURG LIMESTONE ( Caryocystites bed). Fort 

 Loudon and Blue Spring, Franklin County, Pennsylvania. 



In the type localities in the Lake Champlain area, this species occurs 

 in the Middle Chazy (Crown Point) limestone. It has been identified 

 in the stratigraphically equivalent Lenoir limestone of east Tennessee 

 and Virginia. 



Collection. U. S. National Museum. 



RAFINESQUINA MINNESOTENSIS (Winchell) 

 Plate XLV, Fig. 4 



Strophomena deltoidea Owen (not Conrad), 1844, Geol. Expl. Iowa, Wis- 

 consin and Illinois, pi. xvi, fig. 8; pi. xvii, fig. 6. 



Strophomena minnesotensis N. H. Winchell, 1881, Ninth Ann. Rept. Geol. 

 Nat. Hist. Surv. Minnesota, p. 120. 



