Bracldopoda of the Cincinnati Gh-oup. '^1 



thougli Prof. Hall obtained, as he says, "but a single specimen near 

 Cincinnati, showing that the shell is comparatively rare," yet it would 

 not be extraordinary for a collector to pick up a hundred specimens 

 in a day, at an elevation of about 34:0 feet, back of Cincinnati. It is 

 found at Hamilton, Butler county, near Lawrenceburg, Indiana, and 

 in Warren and Clermont countie's, showing that it is persistent in its 

 range, which is probably confined between 300 and 500 feet above low 

 water. It is rather more abundant than its associate, 0. iMcatella, 

 from which it may readily be distinguished by its divided costse. 



OHliis triplicatella — (Meek, 1873). 



This'forra has some resemblance to fissicosta, and some to plieateUa. 

 Prof. Meek says, it has the "same form, coarse costse, and general 

 appearance of 0. plicatella, but differing in attaining a larger size, and 

 in having the area of the ventral valve decidedly lower, and the beak of 

 the same more incurved than in any well characterized specimen of 

 that form. It also differs in having the costse much more widely sep- 

 arated by deeper furrows, and each giving off a small lateral division 

 from near the middle of the valves; the main ones, however, continu- 

 ing larger and more prominent to the free margins, thus forming 

 bundles of three ribs, with a wide, deep depression between." The 

 internal characters still remain unknown, and the only specimens I 

 have seen are those I sent to the Smithsonian, for Prof. Meek's study. 

 I believe, however, that it is a distinct species for one reason more than 

 those urged by Prof. Meek. Large fissicosta and plicatella have thick, 

 firm shells, while these specimens appeared to have rather light, thin 

 shells. It may be only a variety of fissicosta. 



Largest specimen— breadth, 1.04 inch ; length, 0.70 inch ; convexity, 



0.40 inch. 



Found up lime-kiln hollow, in Cincinnati, at an elevation of about 

 350 feet above low water-mark, associated with fissicosta. 



Orthis feeKitk— (James, 1873). 



Shell very small, longitudinally semi-oval, or transversely sub-oval, 

 moderately gibbous, sub-equivalve ; breadth always greater than the 

 length ; hinge line a little less than the greatest breadth of the valves ; 

 posterior lateral extremities abruptly rounded, or sub-angular ; lateral 

 margins rounding to the front, which is broadly semi-el^ptic in outline, 

 or sometimes a little straightened, or even very faintly sinuous at the 

 middle. Interior unknown. 



