284 PROOEEi>rx<;s op the academy of [1889. 



LOWER CARBONIC GASTEROPODA FROM BURLINGTON, IOWA. 

 BY CHARLES R. KEYES. 



Inquiry has disclosed the remnants of an exceedingly rich and 

 varied fauna that, in the vicinity of the present city of Burlington, 

 Iowa, once tenanted the littoral zones of a vast Carbonic sea. The 

 peculiar lithologieal characters of the depositions are not, however, 

 conducive to the good preservation of the entombed animal remains; 

 and, for the most part, the vestiges of the gasteropoda are, in con- 

 sequence, almost entirely obliterated. Nevertheless, there have 

 been obtained a considerable number of shells the structural 

 characters of which are unimpaired and exhibit in a very satis- 

 factory manner all the generic and specific details. These reveal a 

 very suggestive chapter in the faunal history of the early Carbonic 

 over the broad interior basin. 



More than a quarter of a century has passed since the mollusca of 

 the Kinderhook and Burlington beds have elicited attention. The 

 early investigations of Hall, White and Winchell brought to light 

 numerous interesting forms, the greater portion of which were 

 collected in the immediate neighborhood of the locality mentioned. 

 But since the appearance of the original descriptions of the fossils 

 contained in these rocks, there has accumulated considerable 

 additional material, which elucidates some hitherto-obscure questions 

 relative to the zoological position of the various species and their 

 distribution in time and space. 



D. D. Owen l was the first to call attention, geologically, to the rocks 

 exposed at the city of Burlington. In his general stratigraphic section 

 of the region he distinguished the upper calcareous or "Encrinital" 

 layers from the lower shaly portions which he called the argillo- 

 calcareous group. His line of demarkation coincided approximately 

 with that of the present Kinderhook and Burlington divisions — 

 about fifteen feet above the fossiliferous sandstone. Owen correctly 

 referred these rocks to the age of the lower Carbonic. Shortly after 

 the appearance of the report on the geology of Wisconsin, Iowa and 

 Minnesota, Hall, 2 in his reconnaissance of eastern Iowa, referred the 

 arenaceous member (Kinderhook) to the Chemung and regarded as 

 synchronous the yellow sandstones at the mouth of Pine creek, 



1 Geol. Sur. Wis. Iowa and Minn., 1852, p. 91. . 



2 Geol. Iowa, Vol. I, p. 88, 1858. 



