176 PALAEONTOLOGY OF KENTUCKY. 



The columella is much extended below. Suture small and shallow, between 

 the upper volutions scarcely noticeable. The surface appears, to the naked 

 eye, entirely smooth, but under a magnifier shows fine, transverse striae, closely 

 set between some stronger marked lines of growth. These striae and lines of 

 growth extend from the suture down and backwards to the umbilical depres- 

 sion. The last volution, or the body-whorl, as it is also called, curves very 

 abruptly at its middle, and slopes from there in a straight or slightly curved 

 line to the inner lip of the aperture, making the lower half of the last volution 

 either flat or only very little convex. The apex appears to be very minute in 

 perfect specimens. Figure 4 I consider to be the normal form, while figure 2 is 

 either an aberration or the result of a slight compression. 



Formation and Locality. This species occurs in the rotten hornstone of the Devonian formation 

 and was found by Dr. E. S. Clark in the Devonian clay topping the Niagara rocks east of the city of 

 Louisville. I name this heretofore undescribed species in honor of Dr. Clark. 



Callonema imitator. HALL AND WHITFIELD. 

 Plate XX., figures 12 and 13. 



Pleurotomaria imitator, H. and W. 24th Eegent's Ileport, p. 195 1872. 

 Pleurotomaria imitator, H. and W. 27th Eegent's Report, pi. 13 1875. 

 Callonema imitator, Hall. Pal. N. Y., Vol. 5, par2, p. 521879. 



Shell of large size, sub-hemispherical ; spire moderately elevated, consisting 

 of four or five rounded volutions, regularly increasing from the apex to the 

 aperture, which is sub-circular ; rounded below and broadly umbilicate ; suture 

 distinct, not channeled, situated at the periphery of the preceding volution. 

 Surface of the upper sides of the volution marked by strong ridges, which 

 have a slight bend just below the suture, and thence curve backward to the 

 periphery, gradually increasing in strength from apex to outer volution, 

 on the middle of which they are in the ratio of about twenty to an inch; 

 on the outer half of the last volution they become gradually obsolete, or 

 merge into the lines of growth, which also mark every part of the surface. 



Below the periphery there are apparently none of the ridges existing. This 

 species is very similar to Pleurotomaria lucina in form, being a little more 

 depressed, and the volutions less rapidly increasing. The surface-markings 

 are more nearly like those of Pleur. arata, while the volutions are more ventri- 

 cose on the upper side, and the periphery is apparently destitute of a band or 

 sinus, which is a distinguishing feature. 



Formation and Locality. In the rotten hornstone of the Corniferous group, in Jefferson county, 

 Ky., and in Clark county, Ind. Earely found. Only a few specimens are known 'outside of Dr James 

 Knapp's collection. A good interior cast is in my own cabinet. 



