Silurian Fossils. 31 



Kokomo limestone, in the thin-bedded cherty layers at the 

 top of the old ■George W. Defenbaugh quarry, southeast of 

 Kokomo, Indiana. 



Closely related to Isochiliiia graiidis-latiniargiiiata, Jones, 

 but distinguished by the much more oblique postero-dorsal 

 margin, the less extended anterior margin, and the distinct 

 tubercle immediately anterior to the muscular tubercle. 



Beyrichia lata — TRiPLiCATA, Focrstc. 

 Plate I, Fig. 4. 



Closely related to Beyrichia lata, Hall, from the Clinton 

 at New Hartford, in Oneida county. New York, where that 

 species occurs both in the ferruginous shale associated with 

 the iron ore and in the underlying ferruginous sandstone. 

 Calymene cliutoni occurs in the iron ore beds in Herkimer 

 county, and in the overlying shale in Cayuga county. Houw- 

 laiwtus and Dalmanites occur as low as the ferruginous sand- 

 stones associated with the iron ore at New Hartford. 5^3'- 

 richia lata-triplicata occurs associated with Calymene cliu- 

 toni, Vanuxem, in the upper part of the Crab Orchard shales 

 at numerous localities in Lewis county, Kentucky. The 

 types were found between A'alley and the \V. H. Lawrence 

 store. 



Beyrichia lata-triplicata: anterior margin less convex than 

 the posterior margin, with the greatest curvature nearer the 

 ventral margin. The ventral margin usually distinctly curved 

 but sometimes more or less straightened along the middle. 

 Anterior lobe large, ovate, distinctly connected at the base 

 with the attenuated lower end of the narrow middle lobe. 

 The posterior lobe in some specimens appears to unite at 

 the base with the anterior lobe, in others its attenuated base 

 appears to continue for a short distance beyond the point of 

 junction of the other two lobes. The highest part of the 

 posterior lobe forms a ridge immediately in front of the 

 furrow separating the posterior and middle lobes. From 

 this ridge the surface of the posterior lobe slopes toward the 



31 



