170 PALAEONTOLOGY OF KENTUCKY. 



and marked by the retrorsely curving striae, which are less prominent upon it 

 and the adjacent parts than near the suture. Suture close. 



The dimensions and general size of the shells belonging to this species are 

 given in the illustration, which shows the natural size of the specimen from 

 which it was made. 



The specimen before me is an internal cast, but it is covered by a thin coral 

 bearing on its whole surface small tubercles, as shown in the illustration, but 

 not placed with such a regularity as the draughtsman has given them in the 

 figure. This incrusting, tuberculose coral was mistaken for the real shell of 

 the fossil. 



Formation and Locality. Found in the cherty layers of the Devonian formation at and around 

 the Falls of the Ohio, in Kentucky and Indiana. 



Mlirchisonia petilla. HALL AND WHITFIKLD. 



Plate XXXI., figure 5. 



Murchisonia petilla, H. and "W. 24th Eegent's Rep., p. 186 1872. 

 Murchisonia petilla, H. and W. 27th Regent's Rep., pi. 13 1875. 



Shell small, spire elevated, slender and regularly tapering from base to 

 apex ; volutions about twelve gently and regularly expanding from the apex ; 

 moderately convex, somewhat obtusely subangular below the middle ; last one 

 scarcely ventricose. 



Aperture sub-rhomboidal. Surface not known, the specimen being an ex- 

 foliated internal cast. Length of the specimen one inch ; diameter of last volu- 

 tion seven-twentieths, and height one-fifth of an inch. 



Formation and Locality. Occurs in the lower strata of the Niagara rocks in the quarries east of 

 the city of Louisville. The specimen illustrated and described is, so far, the only one known; it belonged 

 to the collection of the late Dr. James Knapp. 



Genus Pleurotomaria. 



Do France. 



Pletirotomaria, De France. Diet. Sci. Nat., 41 1826. 



Etymology: pleura, side; tome, cut or notch, having a deep cut or notch in the outer lip. 



Shells spiral, trochiform, solid, few-whorled, with the surface variously 

 ornamented ; aperture subquadrate, with a deep slit in its outer margin. The 

 part of the slit which has been progressively filled up forms a band round the 

 whorls or volutions. This slit, in the outer lip of the aperture, on which the 

 name has been founded, is seldom visible, as specimens are rarely found per- 

 fect ; but the peculiar bending of the transverse striae, curved backwards to 

 and marking the line of the slit, are always a prominent character of this 

 genus. (Copied from Woodward's Manual and Portlock's Report on London- 

 derry.) 



