MARYLAND GEOLOGICAL SURVEY 265 



reaching the free margins ; the striae starting at and near the beak more 

 prominent than the branching ones ; crossed by very fine concentric lines, 

 visible only under a good magnifier, and even then in some cases quite 

 obscure. Visceral space very little, the valves being so closely drawn 

 together, translucent. Interior not observed. Breadth of a full-sized 

 specimen, 5/8 inch; length, 1.2 inch." Foerste, 1914. 



Although hitherto unfigured the species has long been known as an 

 interesting shell of the Cincinnati area where it occurs at several horizons 

 in the Eden shale and in the Fairview formation of the Maysville group. 

 The above description was based upon the type specimens and the ex- 

 amples illustrated were identified by the author of the species. 



Occurrence. MARTTNSBURG .SHALE (Eden division). Jordans Knob, 

 one and one-half miles northeast of Fort London, Pennsylvania, and in 

 sandstone fragments on Eidkard Mountain, Washington County, 

 Maryland. 



The Orthorhynchula bed at the top of the Fairview division of the 

 Martinsburg shale, just under the Oswego sandstone, one and one-half 

 miles southeast of McConnellsburg Pennsylvania, has furnished numerous 

 specimens. 



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



KAFINESQUINA ALTERNATA (Emmons) 



Plate LVII, Fig. 8 



Strophomena alternata Emmons, 1842, Geol. New York, Kept. 2d Dist., 



p. 395, fig. 3. 

 Leptaena alternata Hall, 1847, Pal. New York, vol. i, pp. 102, 286, pi. xxxi, 



fig. 1; pi. xxxi A, fig. 1; pi. Ixxix, fig. 2. 

 Raftnesquina alternata Hall and Clarke, 1892, Pal. New York, vol. viii, pt. 1, 



p. 282, pi. viii, figs. 6-11, 27, 28; pt. 2, 1895, pi. Ixxxiv, figs. 17, 18. 



Description. " Broadly semioval ; length and breadth about as 12 to 

 15; hinge line, in perfect specimens, a little longer than the width of the 

 shell, slightly reflected at the extremities, which sometimes become short, 

 acute ears ; cardinal area narrow, the callosity of the ventral valve nearly 



