PALAEONTOLOGY OF IOWA. 721 



Pleurotomaria tabulata. 



PLATE XXIX. FIG. 12 a, b. 



Turbo tabulatus : CONRAD, Transactions of the Geological Society of Pennsylvania, 1835, 



Vol. i, pa. 267, pi. 12, f. 1. 



Pleurotomaria tabulata : CONRAD, Journal of the Academy of Nat. Sciences, Philadelphia, 



1842, Vol. viii, p. 272. 



Compare Pleurotomaria virgulata, DE KONINCK, Description des Animaux fossiles, 1844, 



pa. 375, pi. 32, f. 4, and pi. 35, f. 1. 



SHELL turreted, conical. Volutions about eight or nine, 

 angular, somewhat rapidly ascending; the last one ventri- 

 cose, carinate on the outer margin, with a prominent crenu- 

 late or nodiferous band, above and below which the volutions 

 are sometimes a little concave. Suture well defined : aperture 

 transverse, somewhat ovate ; columella thickened ; umbilicus 

 none. 



SURFACE marked by conspicuous striae which are parallel 

 to the lines of growth, bending abruptly backwards on the 

 angulated periphery of the volution : these are crossed by 

 revolving striae which sometimes become slightly nodulose 

 near the sutures of the upper volutions, while on the lower 

 side of the last volution they are more conspicuous, and are 

 cancellated by the vertical striae, becoming nodulose at the 

 junction. 



This species has been referred to P. virgulata of DB KONINCK; but our shell is 

 larger and more robust, and the revolving striae are much less prominent on the 

 upper volutions. The species has a wide distribution, being known from Pennsylva- 

 nia to the Mississippi river. 



Fig, 12 a. View of the anterior side of a large individual. 



Fig. 12 b. View of the aperture, which is imperfect. The specimen figured has the striae 



much obliterated, and these surface characters are not represented as 



they exist in other specimens. 



Geological formation and localities. In the Coal measures of Pennsylvania, 

 Indiana and Illinois. 



[ IOWA SURVEY.] 91 



