NICKLES AND BASSLER.] 



GEOLOGIC DISTRIBUTION. 



73 



SUCCESSION OF BRYOZOAN FAUNAS. 



The subjoined table is desij*'ned to show the succession of y)ryozoan 

 faunas. The formations in the same column do not always have the 

 same taxonomic rank, as now generally regarded. It is to be noted 

 that usage in such matters is not uniform and is pro))ably in a transi- 

 tional stage. 



Table shmving the occurrence of bryozoa by formations. 



Neocene / Pliocene f Not many known in 



I Miocene North Ameriea: 



I very abundant in 

 Eocene \ Europe. 



Cretaceous A moderate number 



known. 



Juratrias None known. 



Permian A limited number. 



Upper Coal Mca.su re.s i 



„ , ,, > A fair number. 



Lower Coal Mea.sures ) 



Conglomerate None known. 



Cpper 



Carboniferous . 



Mississippian . 



Devonian. 



Silurian (Upper) 



Ordovician . 



Cambrian 



Chester 



Middle (Lyropora beds) . . . 



Lower (Kaskaskia lime- 

 stons). 



Big Clifty (=Aux Vases) 

 sandstone. 



Abundant. 



None known. 



St. Louis 



V Abundant. 

 I Few. 



Ste. Genevieve limestone.. A fair number. 



St. Louis limestone Rather few. 



I Warsaw beds 



i Keokuk 

 Upper Burlington 

 Lower Burlington 



IChoteau limestone . . . 

 Hannibal shale \ Very few known. 

 Louisiana limestone j 



Chemung Very few known. 



Hamilton ■> 



TT TT ij I, { Abundant. 



Upper Helderberg I 



Oriskany Very few know n. 



Lower Helderberg Abundant. 



Onondaga None known. 



Lockport' 1 



I Abundant. 

 Rochester ' I 



Clinton and Anticosti A moderate number. 



y Medina None known. 



I Richmond 

 Lorraine 

 Utica 



f Trenton 



Trenton ■! Black River 



I Stones River 



Chazy A few known. 



Caleiferous None known. 



Do. 



Niagara . 



■ Very ul)undant. 



' Names adopted by the United States Geological Survey for formations formerly called Niagara 

 limestone and Niagara shale, respectively. In this work the term Niagara refers to these two forma- 

 tions taken together and excluding Clinton and Medina. 



