FOSSILS OF THE COAL MEASURES. 595 



This species may lc readily distinguished from any other known in 

 the Coal Measures, from its sinus-like, longitudinal depressions and 

 the spines upon its surface. 



1'oxltion and localifi/ Hoof shales of Coal Xo. I); near Brighton, Illi- 

 nois. 



NATICOPSIS SUBOVATUS, Worthen Ms. 



PI. 28, Fig. 9. 



SHELL of medium size, ovate in outline, whorls about 

 three, spire flattened, and occupying about one-third of the 

 entire length of the shell. Columellar lip thickened by a 

 broad, flat callosity, indistinctly striated longitudinally. 

 Outer whorl regularly ventricose, and indistinctly granu- 

 nlose on the surface. 



This species differs from the preceding, as well as from JV. Alton- 

 r//.v/.v, in having its suture less strongly defined, its spire more flattened, 

 and in not having any flattening or depression in the outer volution 

 below the suture, and in the absence of the transverse strife upon the 

 surface. 



Associated with this shell we found two or three specimens of tin 

 opercula. that we have suspected may belong to this species, and there- 

 fore have figured them in connection with it, PI. 28, fig. 10. 



Position ami locality Upper Coal Measures; La Salle, Illinois. 



NATICOPSIS WHEELERI, Swallow's sp. 



PL 28, Fig. 3. 

 -7 WlieelfH. SWALLOW, 1860. Trans. St. Louis Acad. Sci., Vol. I. p. 65a 



Position and locality Upper and Lower Coal Measures; Springfield, 

 Alton and various other localities in Illinois. 



NATICOFSIS ALTONENSIS. 



PL 28, Fig. 11. 



Xittlfa AUonensig. McCiiKsxET ? 1K>5. Pose. Xew Paleo. FOBS. 



jigis Altonentig. same. Trans. Chicago Acad. Sci.. Vol. I. p. 50 ; PL 2. Fig 14. 



Position and locality Limestone below the Hodge's creek coal; Ma- 

 coupin county, Illinois. 



