MISSISSIPPIAN. 409 



The latest statement on the Mississippian is by Weller,^*® whose full discussion 

 may be abstracted as follows: 



WeUer distinguishes (1) a "southern Kinderhook or Chouteau fauna," partly 

 derived from the Devonian (showing relationships to the Hamilton fauna) and 

 partly composed of "a new element from some unknown region." "The return 

 of this fauna into the Mississippi Valley basin marks the opening of the Kinderhook 

 epoch and the Mississippian period." This southern fauna is well developed in 

 southern Indiana and Illinois, in the Rockford limestone of the Indiana State 

 reports. 



(2) A northern Kinderhook fauna, differing markedly from the southern, 

 typified by the "Chonopectus" sandstone and developed in Iowa and northern 

 Illinois, north of the "Kankakee peninsula." This northern fauna is related to 

 the Chemung faunas of the eastern upper Devonian. The southern and northern 

 Kinderhook faunas, though apparently contemporaneous within comparatively 

 narrow limits, occupied distinct faunal provinces as regards invertebrate life. A 

 fish, Ptyctodus calceolus, was common to both. 



During the progress of Kinderhook time the sea was encroaching from both the north 

 and the south, until before the close of the epoch free communication was established between 

 the earlier separated provinces, and the fauna of the southern province became the dominant 

 type throughout the entire Mississippi Valley basin. * * * It is evident that the arrange- 

 ment of the Kinderhook formations into three successive divisions, the Louisiana, Hannibal, 

 and Chouteau, as has usually been done, does not express the proper relationships of the 

 faunas. The Chouteau fauna, in some of its expressions, is without doubt as old as the Louisi- 

 ana fauna, and it is as impracticable to make one continuous section to contain all of the 

 Kiaderhook formations as it would be to make a standard Devonian section to include the 

 formations of New York and Iowa. 



East of the Cincinnati arch the earlj'- Mississippian formation (Bedford shale) 

 carries a fauna which resembles that of the southern Kinderhook. The succeeding 

 formations of the Wavedy group in Ohio are similarly related, but in the north 

 occur forms (Paraphorhynchus) which suggest connection with the northern Kinder- 

 hook also. 



West of the Cincinnati axis the union of the northern and southern provinces 

 gave rise to an extended sea and conditions favorable to the deposition of lime- 

 stones (Burlington and Keokuk) forming the Osage group, characterized by its 

 crinoids. Succeeding formations in the Mississippi Valley basin constitute the 

 Warsaw, Salem [Spergen], St. Louis, and Ste. Genevieve limestones. Unconform- 

 ities follow the Salem [Spergen], and more extensively the Ste. Genevieve, over the 

 northern part of the Mississippi Valley basin. Southern Illinois, where the Ste. 

 Genevieve comprises the Fredonia limestone, Rosiclare sandstone, and Ohara 

 limestone members, was the northern limit of continuous deposition. On the 

 other hand, faunal relations with the faunas of the far West indicate marine con- 

 nections, of which that established during the Ste. Genevieve was one of the most 

 extensive. 



The closing epoch of the Mississippian in the typical province, the Mississippi 

 Valley basin, was that of the Chester group. 



