FOSSILS OF TIIK COAL MKASrKKS. 



distinctly inward from the carina to the suture; lower side 

 of same sloping rapidly inward, and slightly concave just 

 within the prominent nodose ridge, and then rounding 

 rather abruptly into the umbilicus. Surface marked In- 

 distinct lines, and at some places ridges of growth ; on the 

 upper side of the whorls these lines pass obliquely outward 

 and forward from the suture to the carina, thence obliquely 

 backward in crossing the periphery, while in crossing the 

 under side they curve a little backward. 



Greatest breadth of a specimen not quite complete at the 

 aperture. 2.50 inches: bight at the aperture, about 0.84 

 inch. 



J.'"-i(lity <nul position Alton, Illinois; lower Coal Measures. 



STKAPAROLLUS (EVOMPHAI us) SUBQUADKATUS, M. AJ W. 



PI. 29, Fig. 12 and 13. 



( F.uomphalut) subquadraiut, MEEK and WORTHKX, 1870. Proceedings Acad. Nat. Sci., 

 Phila., p. 46. 



SHELL attaining nearly a medium size, discoid or sub- 

 plan-orbicular. concave, and showing all the whorls both 

 above and below, though the concavity is deeper below 

 than above. Periphery nearly flat, rather broad, and more 

 or less oblique, with a distinct carina at the upper and 

 lower edges, the former of which is more acute than the 

 other, and irregularly crenate, or subnodose, and project- 

 ing nearly upward, while the lower one is a little rounded, 

 and projects outward. Volutions five or six, not embra- 

 cing. nor coiled exactly in the same plane; on the upper 

 surface each sloping, with a slight concavity, distinctly in- 

 ward from the marginal carina to the suture, while the 

 flattened outer side usually has an obscure longitudinal sul- 

 i us near the upper and lower angles, the upper one being a 

 little deeper than the other. On the under side the whorls 

 -lope gently inward from the marginal angles so as to form 



