154 GASTEBOPODS. 



Porcellia nodosa HALL. 



Plate li, fig. 4. 



Porcellia nodosa Hall, 1860: Geology Iowa, vol. I, Supp., p. 4. 

 Porcellia nodosa Meek & Worthen, 1868: Geo). Sur. Illinois, vol. Ill, p. 

 458, pi. xiv, figs. la-b. 



Shell large, thin. Whorls about four in number, closely 

 united, circular in cross-secrion, with a dozen or more large 

 nodes on each side of the median plane ; dorsal cleft narrow, 

 deep. Surface marked by fine, regular transverse lines, which 

 are crossed by less prominent longitudinal ones. 



Horizon and localities. Lower Carboniferous, Burlington 

 limestone : Louisiana ( Pike county). 



Cyclomena bilix (CONRAD). 



Pleurotomaria bilix Conrad, 1842: Jour. Acad. Nat. Sci., Phila , vol. 



VIII, p. 271, pi. xvi, fig. 10. 

 Pleurotomaria? bilix Hail, 1847: Pal. New York, vol. 1, p. 305, pi. Ixtxiii, 



figs. 4a-e. 

 Cyclonema bilix Hall, 1852.: New York State Cab. Nat. Hist., 12th Ann. 



Rep., p. 74. 

 Cyclonema bilix Meek, 1873: Geol. Sur. Ohio, Pal., vol. I, p. 151, pi. 



xiii, figs. 5a, c, d, g. 

 Cyclonema bilix White, 1881 : Geol. Sur. Indiana, 10th Ann. Kept , p. 492, 



pi. ii, figs. 3-4. 



Shell variable in form, subglobose to subconoid. Volu- 

 tions about five in number, increasing rapidly in size, mode- 

 rately convex, with a decided tendency to flattening on the 

 upper side, parallel to the general slope of the spire the last 

 volution being rather sharply rounded ; suture well defined. 

 Aperture broadly oval or subquadrate ; inner lip thickened ; 

 outer lip thin, short. Surface marked by revolving lines, which 

 are crossed by oblique lines parallel to the lines of growth. 



Horizon and localities Lower Silurian, Trenton lime- 

 tone: McOune (Pike county). 



Anomphalus rotulus MEEK & WORTHEN. 



Anomphalus rotulus Meek & Worthen, 1866 : Proc. Acad. Nat. Sci., Phila. r 



p. 268. 

 Anomphalus rotulus Meek & 'Worthen, 1873: Geol. Sur. Illinois, vol. V, 



p. 597, pi. xxix, fig*. lOa-c. 

 Anomphalus rotulm Keyes, 1888: Proc. Acad. Nat. Sci., Phila., p. 241. 



