FORAMINIFERAL OOZE IN THE COALMEASURES 



OF IOWA. 



Last summer the writer gathered a number of specimens of 

 the marls, shales, sandstones, and limestones from the Missourian 

 stage of the coalmeasures in Fremont and Mills counties in Iowa. 

 It was desired to study more closely their mechanical structure. 

 A number of the samples were cut and polished, and many were 

 crushed and washed, and the fragments separated by means of a 

 series of sieves, and then examined under the lens and the 

 microscope. In the course of this work several minute fossils 

 were observed that would otherwise have escaped my attention. 

 Among such were various apparently chitinous denticles and 

 plates of brown color, some resembling in form the jaws of 

 Nereidavus, described from the Devonian, and other forms, 

 more frequent, resembling fragments of the radulse of gastero- 

 pods. 



More frequent still were several kinds of foraminifera, such 

 as an Endothyra, a Textularia, and an Ammodiscus. The deli- 

 cate tests of these little animals were found to be quite generally 

 distributed through the whole section of the Missourian in these 

 two counties, excepting arenaceous strata. In rocks which had 

 been leached and weathered they were not to be found. Such 

 frail shells are evidently the first to suffer from oxidation and 

 leaching. 



The upper part of one ledge of limestone was found to be 

 really an indurated ooze composed almost wholly of the shells 

 of an Ammodiscus. It consisted of microscopic tubes, irregularly 

 curved and twisted. The rock might be described as consisting 

 of a feltwork of such tubes, with the interstices filled with trans- 

 parent compact calcareous material. This ledge is in the upper 

 part of the main quarry rock in the bluffs in section i6 in Lyons 

 township in Mills county. It was also noted in the same posi- 

 tion in these ledges in the bluffs, six miles farther south, in sec- 

 tion 14, Scott township, in Fremont county. It has a thickness 



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