IOWA ACADEMY OF SCIENCES. 85 



lying between the Pawnee limestone of the Henrietta and 

 the Bethany limestone of the Missourian series. Haworth* 

 has recently called the shales in question the Pleasanton, from 

 a town in southeastern Kansas. Swallow, f thirty years before, 

 appears to have had essentially the same idea when he defined 

 the " Marais des Cygnes Coal Series." For both, the type 

 localities are practically the same. The recognized basal limit 

 of the one is identical with the other. With very slight change 

 of idea the upper limitations of the Marais des Cygnes could 

 be considered as coinciding with the base of the Bethany, the 

 same as in the case of the Pleasanton. The great thickness 

 ascribed to the Marais des Cygnes is manifestly due to repe- 

 tition of the upper part of the section. But Swallow himself 

 recognized the probability of this fact when he stated that 

 " some of the strata may be duplicated in this series, as they 

 are very much disturbed where the sections were made. ' ' He 

 also said of certain localities that it was almost impossible to 

 make correct sections. 



It is also not improbable that, owing to the lack of good out- 

 crops in this level country, Swallow mistook, in his correla- 

 tions, a part of the Thayer shales for the beds underneath the 

 Bethany, just as he did in the case of what are known to be 

 the Lawrence shales. The correlations of Swallow are in 

 a notable degree faulty, as we now well know. The typical 

 localities of his Marais des Cygnes are all east of the Bethany 

 escarpment, confirming clearly that there was actually a dupli- 

 cation of beds in this part of his section, as he suspected. 



For the strata lying between the Pawnee, the upper mem 

 ber of the Henrietta, and Bethany limestones, Haworth and 

 KirkJ first suggested the name Laueville shales. This term 

 was not defined in any way. Subsequently Haworth, § with- 

 out the slightest reference to this title, and without a very 

 much better definition for the new name, changed it to Pleas- 

 anton shales. In a still later publication || the latter term was 

 more clearly limited. Laneville was then used in a new sense. 

 Again, within a few months, Haworth relegates Pleasanton to 

 a subordinate taxonomic position, placing it and the Henrietta 



* Kansas Univ. Quart., Vol. Ill, p. 274, 1895. 

 + Kansas Geol. Sur., Prelim. Kept., p. 22, 1866. 

 % Kansas Univ. Quart., Vol. 11, p. 108, 1894. 

 § Kansas Univ. Quart., Vol. Ill, p. 274. 1895. 

 II Univ. Geol. Sur. Kansas, Vol. I, p. 153, 1896. 



