126 PALEONTOLOGY OF KENTUCKY. 



groove along their center, a feature most common on the ventral valve. Near 

 the lateral and basal margins there are several strong concentric lines of 

 growth, which give to that part of the surface a strongly imbricate character. 

 This shell is subject to many and extreme variations in the extent of the hinge- 

 line, convexity of the valves, height of area, and the incurving of the beak. 



Formation and Locality. Occurs in the Corniferous limestone at and around the Falls of the Ohio 

 in Kentucky and Indiana. It is an exceedingly rare species in our rocks ; only few specimens have been 

 found in Clark county, Indiana. 



Spirifera mucronata, CONRAD. 



Plate XXXI., figures 10 and 11. 



In the collection of the late Dr. James Knapp was a Spirifera showing the 

 closest resemblance to Spirifera mucronata. The Doctor claimed that he found 

 it somewhere between Watson's Station 'and Charlestown, in Clark county, 

 Indiana. When he found it, he directly identified it as Spir. mucronata, and 

 being aware of the fact that this species had never been found here, he 

 marked it as soon as he reached home. I am fully convinced that the Doctor 

 found the specimen as he stated, but it is possible that the specimen was not 

 a Spir. mucronata. 



The Doctor loaned the shell to me for illustration, but he took it away before 

 I had time to examine it more carefully. Thus I had no opportunity to gain 

 access to the specimen in question, and I am, therefore, not able to give a 

 description of said shell. If it is really a Spir. mucronata, it is certainly the 

 first one ever found in our rocks. 



Spirifera oweni. HALL. 



ft ' 



Plate VII., figures 1 to 10. 

 Spirifera oweni, Hall. Pal. N. Y., Vol. IV., page 197, pi. 29, figures 1 to 8. 



Shell more or less ventricose in its different stages of growth, somewhat 

 transversely Oval, semi-elliptical or sub-quadrate; hinge-line about equal to 

 width of shell; cardinal extremities rounded or angular. Surface plicated. 



Ventral valve scarcely as gibbous as the dorsal valve, its greatest convexity 

 above the middle of its length, and curving regularly to the margins; beak 

 much elevated above that of the opposite valve, and arching over the fissure, 

 but scarcely incurved ; mesial sinus shallow, concave, usually well defined, and 

 reaching distinctly to the apex. Area high, concave, elevated and continuing 

 to the hinge-extremities ; foramen or fissure large, reaching to the apex, and 

 sometimes partially filled by the thickening of the dental plates. 



Dorsal valve the more gibbous, the greatest convexity in the middle, and 



