Contributions to Paleontology. 367 
Miocene, and the fossils of each epoch (except the Eocene) 
are arranged according to their structural aflinities—or rather, 
we should say, as those have been interpreted. Of Jurassic spe- 
cies, 35 are enumerated; of Cretaceous, 885; of Hocene, 766; 
Oligocene, 105, and of Miocene, 775,—a total of 2566 species of 
extinct Invertebrates of the Secondary and Tertiary ages: to 
this number must be added previously undescribed species, whose 
geological or zoological relations were undetermiuable, as well 
as numerous Cretaceous and Tertiary types since described. 
From this total are also excluded the species discovered in the 
tology of the Upper Missouri published since the list, and therein 
is added. 
* This is the first attempt hitherto made, to group our Cretaceous and Jurassic 
Invertebrates, in accordance with their zoological affinities. ee 
