54 GEOLOGICAL FORMATIONS 



is a three-fold division, the upper and lower being limestones 

 and the middle one clay or sandy shale. At Burlington the 

 fossils heretofore noted have been found in the upper portion 

 of the formation ; though very recently an extensive and inter- 

 esting fauna has been discovered in the clayey portion much 

 lower down. Here the lower calcareous member is not ex- 

 posed. At Louisiana and vicinity the median member is prac- 

 tically unfossiliferous, as is also the lower, except at the very 

 base. 



It will be recalled that Marion and Pike counties, Missouri, 

 at Hannibal, Louisiana and Clarksville principally, were the 

 leading localities for a large proportion of the " Kinderhook" 

 fossils originally described by Shumard, Hall, White and Win- 

 chell. It will also be noted that most of these forms have a 

 very decided Devonian aspect which gives a peculiar and char- 

 acteristic physiognomy to the faunas of the three beds. Here- 

 tofore little mention has been made concerning the exact 

 horizon of the fossils in question, mere reference to the 

 "Lithographic" limestone or Kinderhook beds being con- 

 sidered sufficient. Lately, however, extensive collections of 

 fossils have been made at all three places just mentioned, as 

 well as many intervening and neighboring exposures. Every- 

 where the Lithographic or Louisiana limestone has been found 

 to be essentially devoid of organic remains, except an occa- 

 sional form in the thin sandy partings above the bottom- 

 most layer, which is less than one foot in thickness. At the 

 very base of the limestone is a thin seam of buff, sandy shale? 

 seldom over three or four inches in thickness. This seam is 

 highly fossiliferous. It contains the Productella pyxidata 

 {Hall), Gyrtina acutirostris (Shumard), Ghonetes ornata (Shu- 

 mard), Spirifera hannihalensis (Shumard), and a host of other 

 forms, many indistinguishable from species occurring in un. 

 doubted beds of the Western Hamilton. The sandy seam is 

 underlaid by six feet of dark argillaceous shale, which has been 

 regarded as part of the Devonian " black shale " of the Mis- 

 sissippi basin. This in turn rests upon fifteen or more feet of 

 buff magnesian limestone and oolite, of Upper Silurian age, 

 probably. 



