CARBONIFEROUS SYSTEM. 201 



discoTered in this formation that can be referred to the sub- 

 kingdom Yertebeata; and so far as they have yet been 

 recognized they all belong to the order Selachians. They are 

 referred to the following genera, namely: Cladodus, Helodus, 

 Coclrtiodus(?) (and undetermined species.) 



Of Articulates, only two species have thns far been recog- 

 nized. Both of them belong to the genns PTdllipsia. 



The sub-kingdom Mollusca is largely represented, 

 including the classes Cephalopoda, Gasteropoda, (including 

 Heteropoda,) Pteropoda, Bracldopa, LamelliorancTtioia, and 

 Polyzoa. Want of time has prevented the preparation of a 

 complete list of the genera and species of these fossils. 



The Eadlata are represented by a few Crinoids, usually 

 found in a very imperfect condition, but the following genera 

 have been recognized, namely: Platycrinus, Actinocrinus, 

 Rliodocrinns, BeJiapliiocrinus, and Poteriocrinus. The sub- 

 kingdom is also represented by the coral genera Zaglirentis, 

 Tavosites {?) Leptopora, Syringopora, Aulopora, and CI103- 

 tetes (?) 



The prominent feature in the life of this epoch was mollus- 

 can; so much so in fact, as to overshadow all other branches 

 of the Animal Kingdom. The prevailing classes are Lamelli- 

 brancJiiates in the more arenaceous portions, and Brachiopods 

 in the more calcareous portions. 



No remains of vegetation have yet been detected in any of 

 the strata of the formation. 



So far as Iowa is concerned, it is a fact worthy of notice 

 that fossils in this formation are far more abundant in its 

 southern part, where it is more arenaceous, than they are 

 in its northern part, where it is more calcareous. 



2. THE BURLIXGTON LIMESTONE. 



Syn— EncbihtaIi Limestone of Owen and othees, 



Area and General Characters. It has been shown that the 



Kinderhook beds pass so gradually into the Burlington 



limestone, both by their lithological and palaBontological 

 26 



