1897.] NEW YORK ACADEMY OF SCIENCES. 279 



3. Boone Chert. — This formation consists of a series of inter- 

 bedded strata of cliert and limestone, three hundred to three 

 hundred and fifty feet in thickness, the two materials diflering 

 greatly' in relative amounts in different localities. The lime- 

 stone is generally a light colored crystalline rock composed 

 largely of crinoidal fragments. The whole formation agrees 

 well with the Osage group as developed further north, except 

 that the relative amount of chert is greater. 



4. Spring Creek Limestone and Shale. — This formation has 

 heretofore been referred to the Fayetteville Shale by the Ar- 

 kansas geologists. In the region of its typical development, in 

 the western part of the state, the Fayetteville Shale is separated 

 from the Boone Chert by the Wyman Sandstone, a formation 

 which is absent in the Batesville region. Since the correlation 

 of the black shales and limestones in the Batesville region with 

 the Fayetteville Shale is based wholly on the stratigraphy, and 

 as the stratigraphic column is somewhat dissimilar in the two 

 regions, it is thought best to assign a distinctive name to the 

 formation in the Batesville region, until a comparative investiga- 

 tion of the faunas in the two regions proves it to be wholly or 

 in part the equivalent of the more western formation. 



The Spring Creek Limestone, as typically developed on 

 Spring Creek, two miles west of Batesville, is a black fetid 

 limestone abounding in fossils. East of Batesville, in the vicin- 

 it}' of Moorefield, it is more shaly and attains a thickness of 

 three hundred feet. 



The fauna of the Spring Creek Limestone is unique, and the re- 

 sults of a preliminary study of it have been published by Pro- 

 fessor H. S. Williams.* It contains, besides the remarkable 

 Devonian tj'pes mentioned by Professor Williams, a large pro- 

 portion of species which are typically of St. Louis age. 



5. Batesville sandstone. This formation is a buff, yellow or 

 brown, rather fine grained homogeneous sandstone, ranging in 

 thickness from a few feet to nearl}' two hundred feet. Fossils 

 are comparatively abundant in its lowermost layers, but in the 

 upper portions it is apparently barren of organic remains. 



6. Boston Group. — Lying between the Batesville Sandstone 

 below and the Millstone Grit above, is a series of interbedded 

 strata of shales, limestones, and sandstones, that attains a thick- 

 ness of seven or eight hundred feet. The different beds are more 

 or less constant in their development, and a portion of them are 

 fossiliferous, but the faunas have not 5'et been investigated. 



* On the recurrence of Devonian fossils in strata of Carboniferous age, by H. S. 

 Williams. Am. Jour. Sci. {?>), Vol. 49, pp. 94-101. 



