FAUNAL RELATIONS 287 



from southwest Missouri, which has usually been identified as S. marionensis, is 

 also, I think, S. ceMronatus." 



INTERVAL FAUNAS OF THE OZARK REGION 



On the north w t est flank of the Ozark uplift, where the Interval deposits 

 are wanting, the fauna of the original Chouteau limestone directly suc- 

 ceeds an Ordovician fauna. Farther southward in southwest Missouri 

 intermediate faunas become intercalated. 



It has long been known that faunas comparable to those of the Chou- 

 teau limestone, Hannibal shales, and Louisiana limestone occur in this 

 region. Shumard* and Swallow f early recognized there fossils belong- 

 ing to these zones. The later work of the Missouri Geological Survey 

 throws much doubt on the possibility of the extension of the typical 

 Louisiana into the southwestern part of the state, J though the peculiar 

 fauna of the formation is fully recognized. On the other hand, § it is 

 believed that the Hannibal shales are stratigraphically continuous with 

 the similarly named shales of the southestern part of the state. All later 

 evidence seems to bear out the correctness of this supposition. 



Still more recently Professors Weller , || and Williams H have given the 

 results of their studies of the fossils which they found in the formations 

 of southwest Missouri and northern Arkansas. The most noteworthy 

 horizon below the Burlington limestone is the black Eureka shale. The 

 organic forms recorded from this formation are far too few in number to 

 base any very important or exact faunal correlations. The Eureka ter- 

 rane has been generally regarded as Devonian in age. Both of the 

 authors just mentioned are inclined to put the formation considerably 

 higher up — in the Carboniferous. The first named would have these 

 shales represent the typical Chouteau limestone of central Missouri, while 

 the other would parallel them with the typical Louisiana limestone. 



I can well agree with the views of Professor Williams on this point, 

 but with this explanation. At the time at which Professor Williams wrote 

 the fossils of the Louisiana limestone had never been obtained higher 

 than a few feet above the base of the formation, in the shale layers which 

 there alternate with the lower layers of the limestone. This was the 

 known horizon of w r hat is called the Louisiana fauna. It is really the 

 fauna of the black and green shales underlying. I am not aware that 

 any fossils were ever obtained from any part of the Louisiana limestone, 



♦Missouri Geol. Survey, 1st and 2d Ann. Repts., 1855, p. 103. 

 flbid., Repts. 1855-71, p. 207. 

 • % Missouri Geol. Survey, vol. iv, 1894, p. 52. 

 g Ibid., p. 57. 



B Journal of Geology, vol. ix, 1901, p. 130. 

 If Arkansas Geol. Survey, Ann. Rept. 1892, vol. v, 1900. 



