common in the Lower Mercer and higher Pottsville horizons where 

 it attains a much larger size than in the basal members. 



Horizon and locality. Harrison ore: Jackson County (Locality 1), 

 a. Sharon ore: Lick Run, Scioto County (Locality 2), a. Boggs 

 limestone: near Hopewell P.O., Muskingum County (Locality 26), r. 



Family Pleurotomariidae D'Orbigny 



Representatives of this family are extremely abundant in the 

 Harrison and Sharon ores, and at least four forms, possibly more, 

 are thought to be present. They occur, like the entire assemblage 

 from these horizons, as internal casts, which show the form but give 

 little clue as to the external sculpture. These Pleurotom aria-like 

 forms, which are all small, may prove to be new species, although 

 no definite conclusions can be reached concerning them, unless the 

 examination of more material in the future may reveal something 

 concerning the external markings of the group. In only one species, 

 which is described below, is the surface sculpture preserved in ex- 

 ternal molds. 



Genus Pleurotomaria Shumard 



Pleurotomaria ornatiformis n. sp. 



PI. V, Figs. 9, 10, 11, 12, 13. 



Description. Shell small, height a little less than width; volu- 

 tions moderately convex, angular, and shouldered, marked centrally 

 by a relatively broad, flat zone bounded by two prominent revolving 

 carinae; slit-band situated on the central zone between two smaller 

 revolving carinae; region between the shoulder and the central flat- 

 tened area slightly concave, marked by three or four revolving carinae ; 

 region below the slit-band on the last volution convex, marked by 

 numerous closely arranged carinae; surface also marked by fine, 

 transverse, thread-like lines which turn backward above and forward 

 below the slit band. Aperature unknown. 



Dimensions. As these specimens occur as impressions, most 

 of them very fragmehtal, exact measurements cannot be given. How- 

 ever, judging from the material studied, the dimensions of a typical 

 individual are approximately: height 7 mm., height of last volution 

 4.5 mm., width of last volution 9 mm. 



Remarks. This species at first appears identical with P. gurleyi 

 Meek and Worthen, but may be distinguished by the difference in 

 the position of the slit-band. In P. gurleyi it is situated upon or just 

 above the mesial angle, while in the species under discussion it is on 

 the flat, vertical zone between the carinae. The form is common 

 in both the Harrison and Sharon ores. 



Horizon and locality. Harrison ore: Jackson county (Locality 

 1), c. Sharon ore: Lick Run, Scioto County (Locality 2), c. 



84 



