184 PALAEONTOLOGY OF KENTUCKY. 



specimens, some of the surface-markings remain visible ; the revolving striae 

 are generally the first which become obliterated. This species is very variable 

 in size ; we find specimens as small as half an inch or less, and, again, others 

 measuring even more than two inches. The individuals illustrated on plates 

 19 and 21 are about of average size. 



Formation and Locality. Found abundantly, in even well preserved specimens, however, without 

 the revolving striae, in the rotten limestone of the Corniferous group, in Jefferson county., Ky., and in 

 Chirk county, lnd. 



Flatyostoma lineata, var. callosa. HALL. 



Plate XXI., figure 14; Plate XXII., figures 10 and 11, and Plate XXV., figures 5, and 7. 



Plaiyostoma lineata, var. callosa, Hall. Illust. of Dev. Fossils, Gasteropoda, pi. 9 1876. 

 Platyostoma lineata, var. callosa, Hall. Pal. N. Y., Vol. 5 1879. 



This variety has the general form and also the surface-markings of specimens 

 of the species Plat, lineata, with the exception that in this variety the spire 

 is extremely depressed, scarcely extending above the upper level of the volu- 

 tion of habitation, which is generally called the body-whorl. The aperture is 

 large, sub orbicular, with the peristome slightly sinuate on the upper side near 

 its junction with the preceding volution. The inner lip is marked by a thick- 

 ened callus, not observed in any other specimens ; the callosity extending into 

 the lip below, which thence assumes the ordinary features of the species. 



Formation and Locality. Found associated with Plat, lineata in the rotten hornstone of the 

 Devonian formation, in Jefferson county, Ky., and in Clark county, lnd. 



Platyostoma turbinata. HALL. 



Plate XXI., figures 5 and 6. 



Platyostoma turbinata, Hall. Fourteenth Rep. N. Y. St. Cab. 1861. 

 Plaiyostoma turbinata, Hall. Illust of Dev. Foss., pi. 101876. 

 Plattjosloma turbinata, Hall. Pal. N. Y., Vol. 5, part 2, p. 271879. 



Shell sub-turbinate, sometimes approaching a sub-globose form. Spire de- 

 pressed, or more or less elevated above the outer volution, sometimes nearly 

 on the same plane ; volutions three or four rapidly expanding, the last ex- 

 tremely ventricose, with the lower part projected in the direction of the col- 

 umella, which is much extended. Aperture sub-ovate, broader above, narrow- 

 ing, and often extended below. 



Surface marked by fine, sub-equal concentric striae, crossed by finer revolv- 

 ing striae; the former variously undulated upon the surface, indicating 

 sinuosity in the lip of the aperture at former stages of growth. In older 

 shells the striae become lamellose and often crowded in fascicles. 



Formation and Locality. In the Corniferpus group around the Falls of UIQ Qhio, in Kentucky 

 and Indiana. 



