Burlington Limestone in Northeastern Missouri. 451 



of fossils are almost impossible to dislodge. The layers of this 

 bed contain also considerable amounts of chert in small nodules 

 and nodular bands. When first exposed in quarrying these 

 cherts are very compact, translucent, and breaking with a con- 

 choidal fracture, Upon exposure to the weather these flints 

 quickly slacken like quick-lime to a fine intensely white powder. 

 If examined before the process of disintegration has proceded 

 more than half way the white nodules are found to be charged 

 with fossils, which when taken out cannot be told from plaster- 

 of-paris casts. Before affected by the atmospheric agencies, 

 few or no traces of organic remains can be detected in the cherts. 

 But the} 7 ' actually contain a very extensive assemblage of fos- 

 sils ; and in a perfect state of preservation when collected at 

 the right time. They afford unusual opportunities for both 

 structural and systematic studies ; for many of the features 

 commonly not met with are here found beautifully preserved ; 

 such as the internal characters of crinoids and brachiopods, and 

 the delicate ornamentation in nearly all groups. 



Upon careful comparison of the fossils in the cherts and in 

 the surrounding limestones, so far as is possible in the latter, 

 the fossils are found to be identical to a great extent. More- 

 over, numerous shells and crinoids are found partly embedded 

 in the chert and partly in the limestone, with a sharp line of 

 separation, showing clearly that the siliceous impregnation had 

 been acquired long after the original deposition of the beds, 

 and was not due to a greater silicity of waters in which the 

 calcareous deposits were made. This is in accordance with 

 observations made elsewhere in the Burlington limestone of 

 other localities. 



The faunal aspects of the bed in question (number 13 of the 

 section) are particularly interesting. Some of the more com- 

 mon as well as more important species are enumerated below ; 



Ungula melie Hall. 



Discina Newberryi Hall. 



Terebratula Rowleyi Worthen. 



Productus arcuatus Hall. 



Productus Icevicostus White.' 



Productella Shnmardiana (Hall). 



Rhynchonella Missouriensis Shumard. 



Spirifera peculiaris Shumard. 



Strophomena rhomboidalis var. 



Allorisma Hannibalensis Shumard. 



PJdmondia nuptialis Winchell. 



Edmondia Burlingtonensis White & Whitfield. 



Conochardiian sp.f 



Lithophagus occidentalis (White & Whitfield.) 



Aviculopecten cir cuius Shumard. 



