Il8 STUART WELLER 



Mississippi Valley. At intervals this fauna made incursions into the 

 Mississippi Valley Basin, as is evidenced by its representatives in the 

 Kinderhook oolite at Burlington, la., in the Salem limestone, again in 

 the Ste. Genevieve, and to some extent also in the Chester. That this 

 is not a complete interpretation, however, is shown in the occurrence 

 of a group of crinoids described by Miller and Gurley from near Boze- 

 man, Mont.,' which strongly suggests the crinoid fauna of the lower 

 Osage horizons of the Mississippi Valley. It is not improbable that 

 when our knowledge of these faunas in the northwest is expanded, we 

 may be able to recognize elements related to most or all of the faunal 

 divisions of the Mississippi Valley. The evidence at present available 

 suggests that this region occupied a distant part of the same sea which 

 was present farther to the southeast, and that there was more or less 

 unobstructed means of faunal communication between the two regions. 



From the Lake Valley region in New Mexico, there has been des- 

 cribed an early Mississippian fauna^ which is a close ally of the fauna 

 of the Fern Glen formation at the summit of the Kinderhook in the 

 Mississippi River section south of St. Louis. This occurrence idi- 

 cates that the Mississippian sea had transgressed at least as far to the 

 southwest as New Mexico by the close of Kinderhook time, and that 

 means for faunal communication was unobstructed in that direction. 



The Mississippian faunas from Colorado have been described by 

 Girty3 who has reported on materials collected in nine separate regions 

 from the Ouray, Leadville, and Millsap limestones. All of these 

 faunas are separated into two groups by that author, both of which are 

 considered to be of essentially the same age, early Mississippian, 

 probably Kinderhook or early Osage. The composition of the fauna 

 is strikingly like that of the Madison limestone of the Yellowstone 

 National Park, its relationships being especially with the Chouteau of 

 the Mississippi Valley Basin, but the presence of such forms as 

 Eumetria marcyi ?, Straparollus cj. spergenensis, Fenestella serratula ?, 



' Bulletin, 111. St. Mus. Nat. Hist., No. lo. " Poteriocrinus bozemanensis P. doug- 

 lassi, and Plaiycrinus douglassi;" ibid., No. 12. " Batocrinus douglassi, Rhodocrinus 

 douglassi, R. bozemanensis, R. bridgerensis, Plaiycrinus bozemanensis, P. bridgerensis, 

 Dichocrinus bozemanensis." 



2 Miller, Jour. Cin. Soc. Nat. Hist., IV, 306-1^; also Springer, Am. Jour. Sci. 

 (3), XXVII, 97-103. 



3 Professional Paper, U. S. G. S., No. 16. 



