CAEB OSSIFEROUS SYSTEM. 249 



which, B. Americana, is often abundant and it has also been 

 found in the upper part of the Middle coal-measures. 



Mollusks. This sub-kingdom is represented by the 

 classes Cephalopoda, Gasteropoda, LametlibraMcMata, Bra- 

 cliiopoda, and Polyzoa. Ceplialopods are more numerous in 

 genera, species, and individuals, than in any other Iowa 

 formation of later age than the Devonian. Gasteropods and 

 Polyzoans are numerous in species and individual specimens, 

 but Bracliiopods and LameUibrancMates are the most 

 characteristic forms. 



Notwithstanding the fact that the families OrtMdw, 

 Productidw, and Spiriferidtf are approaching the close of 

 their range in geologic time in this formation, they are fully 

 represented here, and their species are among the most 

 characteristic of its fossils. Of the first named family, we 

 find the genera Ortliis, Meeliella, Hemipronites, and Syntri- 

 elasma. Of Productidce — Prodnctus and Clionetes are well 

 represented by several species and numerous individuals, and 

 Aulosteges also by a single small species. The family Bpiri- 

 feridai is represented by the genera Spmfer, Martinia, 

 Atliyris, and Retzia. 



Radiates are much more numerous than in the Lower 

 and Middle coal-measures. Among these are two or three 

 species belonging to the order EcMnoids, and four or five 

 species belonging to the family Cyatliocrinidce. Of corals 

 the genera Campopliyllam, AxopliyUum, Zaplirentis, and 

 Syringopora are not unfrequently met with. 



to and inclu ing a large part of the coal-bearing strata, which we denominate Lower 

 coal-raea-ures. I have visited in person all the Nebraska and Iowa localities from 

 which Prof. Marcou collected the fossils described by Dr. Geinitz, and from all of them 

 I have collected our common species of coal-measure fossils, some of which are com- 

 mon in the Lower coal-measures also, even down among our heaviest beds of coal. 

 The Brachiopods from those Nebraska localities are mainly our characteristic coal- 

 measnre species, while a majority of the species of LameUibrancMates, upon which 

 Dr. Geinitz and Prof. Marcou seem most to rely to prove the Permian age of those 

 strata, I have found far down in the series of Upper coal-measure strata of Iowa. 

 Some of them I have Jound even in the middle coal-measures. It is worthy of remark, 

 that these last named fossils especially, almost always occur in layers having a similar 

 lithological character, the material of which, doubtless, formed a more congenial 

 habitat for them while living, than that which produced the other strata, 



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