30 Cincinnati Society of Natural History. 



CONCHIDIUM COLLETTI, MUleV. 



Common in the upper part of the old George W. Defen- 

 baugh quarry, in the southeastern part of Kokomo, Indiana. 



DiAPHOROSTOMA CLIFTONENSIS, FoeVSte. 



Several specimens closely related to Diaphorostoma clif- 

 tcncnsis, but less strongly elevated, occur in the West Union 

 bed northwest of Martins, in Lewis county, Kentucky. 



ISOCHILINA PANOLENSIS, FoCVStc. 

 Plate I, Fig. 1. 



In the Waco limestone member of the Crab Orchard for- 

 mation, at . Panola and Irvine, Kentucky. 



ISOCHILINA MUSCULOSA, Sp. nOV. 

 Plate I, Fig. 2. 



Carapace large, in one specimen with a length of 8 mm. 

 A better preserved right valve has a length of 6.5 mm., a 

 height of 4.6 mm. ; the length of the hingeline is 4 mm. ; 

 the center of the muscular tubercle is 2.3 mm. from the 

 anterior margin and 1.5 from the dorsal margin. Anterior 

 to the muscular tubercle is a second tubercle, half a millimeter 

 in width and slightly over a millimeter in length. A faint 

 striation crosses the middle of the second tubercle and ex- 

 tends toward the antero-dorsal angle of the valve. Between 

 this striation, the second tubercle, and the dorsal margin, the 

 carapace is slightly elevated, an additional but very narrow 

 elevation occurring at the extreme antero-dorsal angle of the 

 body of the valve. From the groove surrounding the mus- 

 cular tubercle, vascular markings radiate, chiefly toward the 

 ventral margin. A deep depression is on the postero-dorsal 

 side of the muscular tubercle, and a short, narrow, low ele- 

 vation is found along the groove extending postero-dorsally 

 from this depression. A narrow marginal border extends 

 around the anterior, ventral, and posterior sides, widening 

 posteriorly. 



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