LOWER CARBONIFEROUS FOSSILS. 493 



per cent of the fauna of the lowest third of the Madison persists into the 

 upper third, many of the species being of Kinderhook age, or primitive and 

 allied to Kinderhook species; that such genera as Martinia and Seminula 

 range from the very bottom to the top of the Madison; and, in general, the 

 incompleteness of much of the data tabulated, by reason of which the many 

 species known at present from a single horizon, and giving an individual 

 facies to different portions of the series, might on fuller information be 

 found to have a more extended range.. A complete record would doubtless 

 show even less progressive differentiation in the series than now appears. 



The fact that Eumetria vemeuiliana is apparently restricted to the 

 lower beds remains an interesting anomaly. 



I do not believe that the facts warrant an exact correlation of the 

 Madison limestone with the Kinderhook horizon of the Mississippi Basin, 

 although the Kinderhook affinities of its fauna are obvious. The evidence 

 of such genera as Endothyra, Eumetria, Archimedes, and other forms 

 already mentioned, can not be set aside, and the probabilities involved in 

 placing the Madison limestone, 1,700 feet thick, to offset the 300 feet 1 of 

 shales, sandstones, and limestones of the Kinderhook in the Mississippi 

 Valley, are significant. 



A more probable interpretation of the facts observed seems to be that 

 the Madison limestone represents a large portion, possibly even the whole, 

 of the Lower Carboniferous period, being a Kinderhook fauna which 

 through uniformity of conditions of environment had maintained its 

 essential characters long after its contemporary fauna to the east had been 

 superseded. 



This would presuppose a nearly continental distribution of the Kinder- 

 hook fauna during early Mississippian time, which, indeed, we have some 



1 In Missouri the Louisiana limestone (Keyes, 1894, Geo). Suvv. Missouri, Vol. IV, p. 51 et seq.) is 

 said to have a thickness of over 60 feet, the Hannibnl shales or Vermicular sandstone of over 70 feet, and 

 the Chouteau limestone of nearly 100 feet, making a maximum thickness of 230 feet. The same author 

 (loc. cit., p. 46) gives a section at Burlington, Iowa, in which the Kinderhook is given a maximum of 110 

 feet of limestones, sandstoues, and shales. Dana (Manual of Geology, 4th ed., 1895, pp. 637-639) gives 

 the "Knobstono" below the Keokuk in Indiana a maximum thickness of 500 feet. In Michigan the 

 Marshall group, the equivalent in part of the Kinderhook, is said to have 173 feet of grit and sandstones, 

 the overlying Napoleon group having 123 feet of shale and sandstones. In Ohio the Waverly group 

 has a maximum thickness of 1,150 feet, chiefly shales and sandstones (Orton, Geol. Surv. Ohio, Vol. VII, 

 1893, p. 4), or, as is averaged in the same table, 500 to 800 feet. However, Herrick considers a portion 

 of this to be of Devonian age, while the rest represents the Kinderhook, Burlington, and Keokuk 

 periods. 



