14 



NORTH AMERICAN INDEX FOSSILS. 



36. C. missouriensis Swallow. Mississippic. 

 Large, coarse, rapidly tapering; median groove faint or absent; 



marginal grooves deep; transverse ridges sharp, distant, arched, 

 sometimes medially deflected. 



Warsaw and St. Louis of Missouri, IlHnois, Indiana; Missis- 

 sippic of Nevada. 



37. C. byblis White. Mississippic. 



Fig. 1225. Conularia undu- 

 lata, X Vz- 



Fig. 1226, Conularia undulata, 

 enlargement of surface. 



Large ; sides depressed convex ; median groove faint ; transverse 

 ridges narrow, raised, 45-50 to the inch, slightly curved and form- 

 ing obtuse angle at median groove. 



Waverly of Ohio and Tennessee ; Kinderhook of Iowa. 



38. C. subulata Hall. Mississippic. 

 Small (less than i inch long), moderately tapering; apical angle 



about 18° ; ridges nearly flat; no median groove present; transverse 

 striae fine, arched. 



St. Louis of lUinois and Missouri. 



39. C. crustula White. Carbonic. 

 Like the preceding, but more rapidly tapering and with faint 



median groove; length 31 mm. 



Coal Measures of Missouri, New Mexico and Arkansas. 



