FOSSILS OF THE SILURIAN AND DEVONIAN ROCKS. 173 



Pleurotomaria procteri. . *r. 



Plate XXI., figures 9, 10 and 13. 



Compare Pleurotomaria capillaria, var. of Pal. N. Y., Vol. 5, Part 2, text, page 87, and Pleur. capillarin, 

 var. rustica, of Pal. N. Y., Vol. 5, Part 2, Plates, Plate 30, figures 20, 21 and 22. 



Shell trochii'orm ; height exceeding width about one-fourth or more. Volu- 

 tions from five to six, somewhat rapidly increasing in size, the last one ventri- 

 cose ; there is only one carina above and one below the peripheral band : the 

 carina above the band gives to upper portion of the volution a sub-angular 

 appearance, while the lower part is regularly rounded. The peripheral band is 

 divided by a somewhat finer central carina, which is crossed rectangularly by 

 strong striae, which only extend from margin to margin of the peripheral band, 

 with interspaces of about four times their own size. These rectangular striae 

 are entirely separated from the striae of the upper or lower half of the volu- 

 tion ; they give the dividing carina a beautifully crenulated appearance. On 

 both sides of the peripheral band, the siirface is ornamented by strong trans- 

 verse striae ; in the upper half they start from the suture, and run in an almost 

 straight line, with a backward deflection of about ten degrees, to the first carina, 

 from where they curve slightly backward to the upper marginal carina of the 

 peripheral band. This system of striae, interrupted by the band, continues at 

 the lower marginal carina of the latter, from where the striae extend in slightly 

 curved or nearly straight lines with a forward deflection, either to the sutures 

 of the upper volutions, or to the lower carina of the body-whorl. From this 

 lower carina, which forms the suture-line of the upper whorls, and which is, 

 therefore, only visible on the last volution, the striae curve gently to the um- 

 bilicus and to the columellar lip; but a great number of them die out or become 

 extinguished at different distances from the lower carina. All the volutions 

 are, in their transverse section, extremely convex, which gives them very deep 

 sutures, and separates them from each other in a very decided manner. The 

 aperture of this shell is not known, inasmuch as in all the specimens in niy 

 collection the outer lip is missing. 



This species stands between P. sulcomarginata and P. capillaria, both of 

 which it resembles in some respect, but it is easily distinguished from the first 

 by its more elevated spire, its larger size, and the difference in the number and 

 arrangement of the revolving carinae ; from the latter by the greatly smaller 

 number of revolving carinae, and from both here named, and all other species 

 of the genus Pleurotomaria, by the crenulated central carina in the peripheral 

 band, which is very characteristic in P. procteri. 



Formation and Locality. Associated with P. sulcomarginata in the Corniferous limestone of Jef- 

 ferson county, Ky., and of Clark county, I ml. It is a somewhat rare species. This beautiful shell I narno 

 in honor of Kentucky's State Geologist, Prof. John R. Procter, who has served his State with great dis- 

 tinction, and who has labored, more than any other man, to bring the great mineral wealth of Kentucky to 

 the knowledge of the people at large. 



