486 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



Table showing the range of Lower Carboniferous species — Continued. 



Species. 



Number of bed. 



24 



25 



26 



27 



28 



29 



30 



31 



32 





X 



X 



X 



X 



X 



































X 



? 























X 



Seminula madisonensis var. pusilla n. var. 







X 

 X 



X 



X 

 X 







X 

 X 

 X 



X 

 X 



x 





X 





X 





C'liothyris crassicardiualis var. nana n. var. 



X 

 X 



X 



X 



X 



X 



X 



X 







X 













Conocardinm pulchellum (?) 

















































X 

 X 















X 

 X 



X 



X 



X 







X 

 X 

 X 





Proetns peroccidens 





X 































The following data are derived from the table just given, and go to 

 show that the Madison limestone fauna is practically a unit, evincing very 

 little progressive differentiation, and not affording sufficient evidence to 

 warrant its subdivision upon paleontologic considerations. 



Seventy-nine species have been recognized in the nine beds which go to 

 make up the formation. Of these, 4 species have not been assigned to any 

 particular bed, because it has not been ascertained what position the locali- 

 ties from which they came would occupy in the type section. These, with 

 5 species of Platyceras and 5 of Fenestella, have not been taken into con- 

 sideration in collecting the following data. Therefore only 65 species have 

 been considered in making up the tables from which these data are sup- 

 plied. Of these 65 species, 29 are found to be rare and scattered among 

 single beds, but some 17 or 18 are common, and may be said to range 

 from the bottom to the top of the formation. 



If the nine beds constitutino- the Madison limestone be artificially divided 

 into three groups of three beds each, the central group is represented by 38 

 species, only 6 of which are not found in the upper or the lower group, 



