286 U. R. KEYES DEVONIAN INTERVAL IN MISSOURI 



There are also many elements in the lower Kinderhook fauna of teh 

 type locality and in that of the Grassy Creek shales underneath, that 

 induce one to make careful comparison between them and the fauna of 

 the Lime Creek beds of Iowa. 



ROLE OF CERTAIN FA UNAL ELEMENTS 



The biological relationships of certain forms of fossils which appear to 

 have an extended vertical range are of exceptional significance. An ex- 

 ample is found in Spirifer marionensis of Shumard. This brachiopod is 

 the most abundant and characteristic fossil found at the base of the Louis- 

 iana limestone. It ranges upward in constantly diminishing numbers 

 to the top of the Hannibal shales. It has been often reported from 

 higher horizons in southwest Missouri, especially, and at Burlington. 

 The form going under this name as occuring in the Chouteau and its 

 equivalents, does not appear to be Spirifer marionensis at all, but a species 

 which at first glance has the same general appearance as that form- 

 Although the distinction between the two shells has long been recognized, 

 all have been called, in the Missouri reports, by Shumard 's name, because^ 

 in the allusions made, the S. marionensis was a familar form, and absolute 

 exactness or nice identification was not essential to the treatment of the 

 themes then in hand. 



The form in question was thought to be identical with that far-west 

 shell described by White * from Nevada as Spirifer centronatus (not S. 

 centronata of Winchell, 1865). The typical S. marionensis, Shumard, 

 seems to find its closest affinities with certain Lime Creek spirifers. 



That the suspicion of the identity of the so-called Spirifer marionensis 

 from the horizons above the top of the Hannibal shales is well founded 

 is further indicated by a recent statement f of Professor Weller, who is 

 giving special attention to Kinderhook faunal studies. He says : 



" I have been coming to the conclusion strictly from the faunal evidence that 

 the strata representative of the Louisiana limestone at Burlington must be lower 

 down than I had first suspected. I have looked for the Spirifer marionensis fauna 

 at Burlington, and was at first inclined to identify the common spirifer in the 

 oolite bed with this species. This identification led me to place the horizon of the 

 Louisiana limestone higher than I would otherwise have done. I am now con- 

 vinced, however, that S. marionensis does not exist at Burlington, at least in the 

 collections I have been able to study. I now identify this oolite species with that 

 which has been described from the far west as S. centronatus. Whether it is Win- 

 chell's original S. centronatus from Michigan I do not know, having never seen 

 authentic specimens from there and it never having been illustrated. The spirifer 



*Geog. and Geol. Survey, west of 100th Merid., 1877, p. 86. 

 t Communication. 



