Silurian Fossils. 13 



anterior part of which follows the general convex curvature 

 of the shell. Three plications occupy the very shallow sinus. 

 There are five lateral plications on each side, which are in- 

 distinct over the middle and posterior parts of the cast. 

 The anterior slope of the shell is fairly abrupt. There is a 

 distinct median septum in the brachial valve, and there are 

 traces of dental plates in the pedicel valve. 



West Union bed, northwest of IMartins. in Lewis county. 

 Kentucky. 



This shell is much smaller than Caniarotocchia pisa, as 

 figured by Hall and \Miitfield, and may have come from a 

 different horizon. 



WiLSONIA KOKOMOENSIS, MiUcV. 



Described from Kokomo, Indiana, but not found by the 

 writer. 



Atrypa reticularis-xiagarexsis, XettclrotJi. 



A single valve, 10 mm. in length, with six radiating plica- 

 tions in a width of 5 mm., was found at Harin Hill, four 

 miles west of A'alley, also at the Clarksburg chapel, three miles 

 south of A'anceburg. in Lewis county, Kentucky, in the West 

 L^nion bed. 



Atrypa rugosa. Hall. 

 Plate II, Fig. 6: 



A cast of the external surface of the pedicel valve. 10 mm. 

 long. A single plication occupies the sinus. The plications 

 bordering the sinus are rather prominent and bifurcate near 

 the anterior end, but the bifurcations remain close together. 

 Next, on each side, comes an intercalated plication, then a 

 primary plication bifurcating distinctly toward the end, the 

 bifurcations spreading considerably. Then, another interca- 

 lated plication, followed by a primary plication, and one or 

 two smaller plications near the anterolateral margin. The 

 characteristic feature is the presence of both bifurcating pri- 

 mary and intercalated secondary plications. 



13 



