186 PALEONTOLOGY OF KENTUCKY. 



Genus Strophostylus. 



Strophostylus, Hall. Pal. N. Y., Vol. 3, page 3031859. 

 Etymology : strophe, turning around ; stylos, a column. 



Shell sub-globose or ovoid-globose ; spire small, with a large ventricose 

 body-whorl. Outer lip thin, not reflected, sometimes slightly expanded. 



Columella twisted or spirally grooved within ; not reflected. No umbilicus. 

 Aperture somewhat round-ovate or transversely broad oval. 



Strophostylus varians. .HALL. 



Plate XXII., figures 6 and 7. 



Strophostylus varians, Hall. 111. of Dev. Foss., pi. 2 1876. 

 Strophostylus varians, Hall. Pal. N. Y., Vol. 5, pt. 2, p. 311879. 



Shell of medium size, spiral, with moderately elevated spire; volutions 

 about three or four; ventricose and regularly rounded above, and somewhat 

 rapidly increasing, the last one becoming very ventricose, and extending 

 downward and forward. Aperture ovate or sub orbicular ; peristome entire ; 

 the columellar lip usually expanded, and spreading over the umbilicus, some- 

 times free, and leaving the umbilicus exposed. 



Surface covered by fine, closely set, transverse striae, the suture, owing to 

 the great convexity of the volutions, deep and well exposed. Prof. Hall 

 makes the following remarks about this species: u This species, in some re- 

 spects, makes a wider departure from the typical forms of Strophostylus than 

 any other of the genus known to me. The peculiar and characteristic form is 

 preserved ; the symmetrical rounding of the volutions above, and the delicately 

 formed spire, as well as the form of the aperture in some specimens, are all 

 characteristic of the genus. The striae, however, have a tendency to become 

 lamellose or interruptedly undulating ; and there are evidences of irregularity 

 of growth and indentations in the margin of the peristome, both above and 

 below the periphery. The form of the aperture is extremely variable, from 

 narrow elliptical to broadly expanded. There is, though rarely, a tendency in 

 the last volution to become free, and the characteristic plication of the colum- 

 ellar lip is not often well preserved. In some of its variations it simulates 

 Platyostoma, but in all phases it differs from that genus in the characteristic 

 expression of the spire." 



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

 in Kentucky and Indiana; but it is a rather rare shell in our rocks. 



