PALAEONTOLOGY OF IOWA. 649 



FOSSILS OF THE WARSAW LIMESTONE. 



THE Warsaw limestone, though a well-marked and distinct 

 group of strata, nevertheless, as already stated, rarely attains 

 any considerable thickness. In many localities, and over wide 

 areas, it appears to have been deposited in shallow water : it 

 is often oolitic in character, and contains numerous species of 

 Gasteropoda, with many small forms of Brachiopoda, and a 

 great abundance of Bryozoa. 



I have endeavored to present a few of the most charac- 

 teristic forms of each of these families of fossils, limiting the 

 number of illustrations below those given for the preceding 

 rocks, chiefly in accordance with our present views of the 

 importance of the formation, and corresponding somewhat 

 to the number of species known to belong to this rock within 

 an area equal to that from which the fossils of the Burling- 

 ton and Keokuk limestones have been obtained. Some of 

 them have, however, been derived from more distant points ; 

 but as those from Indiana serve to indicate the same horizon, 

 which has been recognized by Mr. WORTHEN as corresponding 

 to that above Alton, and of Warsaw ( Illinois), and which is 

 likewise proved in the southern part of Iowa, it has seemed 

 desirable to illustrate the association of species from strata 

 which are yet but partially investigated. 



[low- A SURVEY.] 82 



