FAUNAL RELATIONS 283 



extending through the whole section of the Louisiana, Hannibal, and 

 Chouteau divisions. Moreover, the ascribed fauna was also found to be 

 a limited fauna of only the upper part of the Kinderhook. With a few 

 exceptions, the forms described as coming from the Kinderhook had 

 been collected from only the uppermost layers of that formation — the 

 Chouteau limestone and its stratigraphical equivalents. Practically no 

 extended examinations of the fossils from the Hannibal shales and the 

 Louisiana limestone had ever been undertaken by the earlier geologists. 

 Generally, these two formations had been reported as barren of organic 

 remains. A few species had, however, been noted from the very base of 

 the Louisiana limestone, but no indication of the real horizon had been 

 given in the descriptions. 



The surprise in store was that both at Burlington and at the original 

 locality (the cities of Louisiana and Hannibal are only a few miles from 

 the village of Kinderhook, but on the opposite side of the Mississippi 

 river) the Kinderhook shales from which no fossils had been reported 

 were well supplied with organic remains, yet forms on the whole very 

 different from those occurring higher up. It was soon seen that the 

 fauna at the top of the Kinderhook formation was entirely distinct from 

 that at the bottom of the section. This fact was made known in a paper* 

 on the " Dual character of the Kinderhook fauna. 1 ' 



The problem of the exact relation of these two faunas demanded im- 

 mediate attention. It was highly important to. discover whether the 

 two faunas gradually merged into each other, or whether the upper one 

 abruptly replaced the lower one at a given horizon. The last-mentioned 

 hypothesis was found to be the fact. In order to carefully determine 

 this point, it was proposed to fix the vertical range of the various species 

 composing the faunas, and thus to see not only exactly at what levels 

 the forms disappeared, began, or replaced others. The splendid Louis- 

 iana section of rocks, of more than 300 feet in vertical measurement, 

 was divided into twenty well marked lithologic platforms. Mr R. R- 

 Rowley, who had long lived in the neighborhood and who had made 

 extensive collections of the fossils, volunteered his services in the work. 

 The results of the investigation are recorded in a joint paper f on the 

 " Vertical range of fossils at Louisiana." Tables give the distribution of 

 each species through the various layers. Out of 500 different forms, not 

 a single one of those occurring in the lower part of the section was found 

 to extend above the base line of the Chouteau limestone. Not a single 

 species found in the upper portion of the section descended below the 

 same level of the Chouteau. The fauna of the upper " Kinderhook " 



*American Geologist, vol. xx, 1897, p. 167. 

 fProc. Iowa Acad. Sci., vol. iv, 1897, p. 26. 



XLII— Bull. Geol. Soc. Am., Vol. 13, 1901 



