8G 



THE CHICAGO ACADEMY OF SCIENCES. 



Galba si in His (Mei 

 Galba diaphana (E. & S.). 

 Galba ncbrasccnsis (E. & S.). 

 C7a/ta meekiana (E. & S.). 

 Galba shumardi (Meek). 

 Galba florissantica (Cockerell). 

 Galba contracosta (Cooper i. 

 Galba alamoscnsis (Arnold). 

 Galba bonncvillcnsis (Call). 

 Galba bakeri (Walker). 

 Galba nashotahensis (Baker). 

 Galba accelerata (White). 



Subgenus POLYRHYTIS 

 Galba king* Meek. 



Middle Eocene. 

 Oligocene. 

 Oligocene. 

 Oligocene. 

 Oligocene. 

 Oligocene. 

 Pliocene. 

 Pliocene. 

 Pliocene. 

 Pliocene. 

 Pliocene. 

 Comanchean. 

 Meek. 



Lower Pliocene. 



II. STRATIGRAPHICAL TABLE OF EXTINCT AMERICAN LYMN.EAS. 



Era. 



Mesozoic 



Period. 

 Comanchean or 

 Lower Cretaceous. 



Cretaceous. 

 Cretaceous. 



r Lower Eocene. J 



Middle Eocene. 



■~ ^ Oligocene. 



Cenozoic. j 



Middle Miocene. 

 Lower Pliocene. 



Upper Pliocene. 



JJ Pleistocene. 



La 



Formation. 

 Atlantosaurus. 

 (Morrison; Como 



Bear River. 

 Laramie. 

 C Fort Union. 



L Wasatch. 

 Bridger. 



White River. 



f 



I 

 LFlorissant. 



Mascall. 



Humboldt. 

 ("Contracosta Lake bed. 



(Merced series.) 

 ) Fernando. 

 I Bonneville beds. 



Anticosti Marl beds. 



Michigan Marl beds. 



Wisconsin Marl beds. 



Species. 

 J ativuncula White. 

 ) i consortis White. 

 ^accelerata White. 



nitidula Meek. 

 f tcnuicosta M. & H. 

 ■{ t. whiteavesi Baker. 

 Vcompactilis White. 

 tcnuicosta M. & H. 

 j tcnuicosta M. & Ff. 

 / minuscula White, 

 f vctusta Meek. 

 \ similis Meek. 

 ( diaphana E. & S. 

 I ncbrasccnsis E. & S. 

 j meekiana E. & S. 

 i shumardi Meek. 



rscudderi Ckll. 

 ^ sieverti Ckll. 

 [ llorissantica Ckll. 



stearnsi Hannibal. 



kingi Meek. 



contracosta Cooper. 



alamosensis Arnold. 

 bonnevillcnsis Call. 

 anticostiana Dall. 

 bakeri Walker. 

 nashotahensis Baker. 



