624 NORTH AMERICAN INDEX FOSSILS. 



Differs from B. leda in its narrower band, less rapid expansion, 

 less pronounced umbilicus and finer striae. 



St. Louis of Indiana and equivalent horizon of Nevada (?). 



69. B. marcouana Geinitz. (Fig. 840.) Carbonic. 



Like B. leda, but with fine, regular, 

 simple striae and rather strong rounded 

 carina, transversely lined. Spirals on 

 band very fine. 



Coal measures of West Virginia, Ohio, 

 Illinois, Missouri, Nebraska, and Arkan- 

 sas. 



70. B. montfortiana Norwood and 



Fig. 840. Bucanopsis mar- p ra tten. (Fig. 834, £-, h.) Carbonic. 



couanus. (After Keyes. ) ou n i_m- 11 u -i.u 



v J ' Shell non-umbihcate, small, but with 



large expanded lip ; band in median depression from each side of 

 which extend large subnodose wrinkles to near the umbilicus, 

 except on the expanded apertural part. Surface with revolving 

 coarser and finer striae, which are somewhat nodose on the ribs. 



Coal measures of West Virginia, Ohio, Indiana, Illinois, Iowa, 

 Missouri, Kansas, Nebraska, Texas, and Utah. 



XXII. »Ptomatis Clarke. 



Like Bellerophon, but with very rapid and broadly expanding 

 lip, which is sinuate in front, and without band ; granulose callus 

 on inner lip, whorls narrowly umbilicate. Devonic. 



71. P. patulus (Hall). (Fig. 841.) Devonic. 



Fig. 84 1 . Ptomatis patulus. ( After Hal 1 . ) 



Smooth, except for growth lines, which on earlier whorls are 

 strong and regularly costate ; callus granulate; sinus very shallow. 



