78 NEW YORK STATE MUSEUM 



miargins nearly equally converging toward the ventral margin, 

 which is subparallel to the cardinal line. Depressed convex, the 

 highest part consisting of an obtuse ridgelike prominence, run- 

 ning across the shell longitudinally and ventrally of the center; 

 from the ridge the valve slopes evenly or with slight concavity 

 toward the thickened cardinal edge. Sulcus rather broad, situ- 

 ated mostly somewhat posteriorly of the median line, and begin- 

 ning a little ventrally of the cardinal line. No distinct node or 

 bulb situated behind the sulcus. Marginal area consisting of a 

 high angular ridge, which encircles the entire lateral and ventral 

 margins of the valve, and which varies somewhat in breadth, but 

 always becomes narrower along the ventral margin, where it 

 abruptty turns downward. Outside of this lies still a narrow, 

 flat, radially striated border, which, however, is mostly broken 

 off. Surface in some specimens very coarsely pitted, in others 

 very faintly so, in most, however, perfectly smooth. Shell very 

 thin, specially the marginal area. 



Dimensions. Length 2.1 mm; hight 1 mm; thickness A mm. 



Horizon and locality. Common in the gray crystalline and com- 

 pact limestone pebbles of the Kysedorph hill conglomerate. 

 (Groups 6, 7) 



Observations. This form has all the essential features 

 of Eurychilina subradiata Ulrich ; it differs only in 

 the absence of the distinct node and the more acute 

 cardinal angles, differences which are of not more than varietal 

 importance, such as the same species is very likely to develop in 

 widely separated regions. Eurychilina subradiata has 

 thus far been found in Illinois, Tennessee, Wisconsin, and Minne- 

 sota, where it is restricted to the Lowville limestone. 



Eurychilina dianthus sp. nov. 



PL 5, fig. 1, 2, 8, 9 



Diagnosis. Valve very thick, suboval, equilateral; cardinal 



line straight, cardinal angles obtusely rounded, anterior 



and posterior margins nearly equally and strongly rounded; 



