GASTROPODA— -BELLEROPHONTIDJE. 



613 



With one obtusely angular ridge on each side, half way between 

 umbilicus and ridge flanking the sinus. A median ridge occurs in 

 the slit band, though often not preserved. 



Stones River of Tennessee ; Black River and Trenton of Min- 

 nesota, Canada, New York, and Tennessee. 



35. T. sexcarinata Ulrich and Scofield. (Fig. 819, e-h, I.) 



Ordovicic. 



Larger, with stronger and more persistent ridges, with an addi- 

 tional one on either side, making six in all. Surface striae strong. 



Stones River of Minnesota, Illinois, and Tennessee, and Trenton 

 of Minnesota. 



36. T. obsoleta Ulrich and Scofield. (Fig. 819, i-k.) 



Ordovicic. 



Revolving ridges obsolete, umbilicus smaller than in T. bidorsata, 

 volutions more rounded. 



Stones River of Wisconsin, Black River of Kentucky and Min- 

 nesota, Trenton of Minnesota, Utica of Cincinnati region. 



XIV. Bucania Hall. (Emend. U. and S.) 

 Bellerophontid shells with generally large umbilicus and de- 

 pressed volutions which do not expand rapidly or abruptly ; aper- 

 tural sinus ending in a slit ; slit-band distinct, raised or depressed ; 

 surface with oblique revolving lines and lines or lamellae of growth. 

 Ordovicic. 

 37. B. sulcatina Emmons. (Figs. 820, 821). Ordovicic. 



Fig. 820. Bucania sulcatina, X %• 

 (After Raymond.) 



FlG. 821. Bucania sulcatina, 



X2- 



Large ; whorls angular at umbilicus, width of aperture about 

 equal to height of shell. Apertural angles acute. Surface with 

 strong revolving and finer transverse striae. 



Chazy of Champlain region. 



