840 E. O. ULRICH CORRELATIONS OF CHESTER FORMATIONS 



by differences in their respective faunas. It is to be noted further that 

 the break between the Gasper and the underlying Sainte Genevieve also 

 is not very clearly defined. In fact, to succeed in making this separation 

 one must use very detailed methods in distinguishing closely allied fossils 

 and employ both physical and organic criteria only too commonly neg- 

 lected or unappreciated by paleontologists and stratigraphers. Moreover, 

 the Sainte Genevieve in these sections also is indivisible by ordinarily 

 employed lithological criteria. One sees nothing of the Kosiclare, the 

 Cypress, or the Sample sandstone, which have proved such valuable indi- 

 cators in subdividing this mass of limestone in western Kentucky. In 

 consequence the whole interval between the Saint Louis below and the 

 Cypress sandstone above have in these sections nothing upon which the 

 observer who is not specially trained in Chester paleontology and stratig- 

 raphy can seize and rely upon in determining the exact age of any part 

 of this series of interbedded oolitic, crystalline, and compact limestones. 

 To meet this condition I proposed the term Montesana limestone for the 

 whole mass, the term to be used in the sense of a group where its sub- 

 division is rendered practicable by punctuating beds of sandstone or 

 shale, and as a simple formational designation where such dividing beds 

 are absent. 



The practice of most paleontological stratigraphers who have made 

 any effort to divide the Montesana as developed in south central and 

 eastern Kentucky, in Tennessee, in northern Alabama, and in the west- 

 ern edge of the southern part of the Appalachian Valley as far north as 

 Big Stone Gap, in Virginia, has been to draw the base of the Gasper as 

 far down in the section as the first observed appearance of a single fossil 

 species, namely, the well-known crinoid Platycrinus huntsvillce. If the 

 observer happens to hold the views espoused by Weller, who classifies the 

 Sainte Genevieve with the Meramec group, and hence with the Iowa 

 series, which, according to Welters new classification, 21 includes all of 

 the Mississippian beneath the Aux Vases sandstone, the boundary thus 

 decided upon forms at the same time also the base of the Chester series. 

 However, to any one whose experience has taught him something of the 

 gregarious habits of crinoids, the highly uncertain nature of the results 

 obtained by this procedure is at once apparent. 



Local occurrence of crinoid colonies. — Eecent experience in searching 

 for crinoids in northern Alabama, will serve as an appropriate illustra- 

 tion. About the middle of the last century Troost listed an undescribed 



11 Stuart Weller : The Chester series in Illinois. Jour. Geology, vol. xxviii, 1020. p. 

 408. Geology of the Golconda quadrangle. Kentucky Geol. Survey, series 6 vol 4 

 1021, p. 13. 



