6 14 NORTH AMERICAN INDEX FOSSILS. 



38. B. halli Ulrich and Scofield. (Fig. 822.) Ordovicic. 



Aperture twice as wide as high. Lateral angles acute. Smaller 

 than preceding. 



Stones River of Minnesota, Black River of Kentucky. 





Fig. 822. Bucania halli. a, b, side and dorsal v'ew ; c, d, sections of whorls. 

 (After Ulrich and Scofield, Pal. Minn.) 



39. B. punctifrons Emmons. Ordovicic. 

 Rather small with large umbilicus and subpentagonal aperture 



slightly wider than high ; slit band somewhat elevated ; surface 

 covered by a meshwork, which gives it a punctate appearance. 

 Trenton of Canada, New York, Tennessee. 



XV. Salpingostoma Roemer. 



Bellerophontid shells, with gradually enlarging, scarcely em- 

 bracing volutions, and abruptly expanding, trumpet-like mature 

 aperture. Inner volutions with a slit band as in Bucania, last half 

 of whorl with long, narrow slit, closed behind the peristome ; sur- 

 face with revolving lines often oblique and wavy, and lines of 

 growth. Ordovicic. 



40. S. buelli Whitfield. (Fig. 823, a-c.) Ordovicic. 

 Of about three and a half volutions, rather large ; gradually ex- 

 panding ; lip flaring out abruptly. 



Stones River and Black River, Minnesota, Wisconsin, and 

 Illinois. 



41. S. expansa Hall. Ordovicic. 

 Subangular, large, of about four volutions, with abruptly ex- 

 panding aperture, and obtusely carinated dorsum. Section of last 

 volution subtriangular, surface striate. 



Trenton limestone of New York, Canada, etc. 



42. S. richmondensis Ulrich. (Fig. 823, d, ,e.) Ordovicic. 

 About three volutions ; the last expanding somewhat more 



rapidly, and the lips flaring less abruptly than in the preceding 

 species. Richmond group of Indiana. 



