38 CRE^TACEOUS PALEONTOLOGY. 



and studied. The numbers in the columns opposite the species 

 name indicate in each case the number of localities from which 

 the species has been recognized, and a comparison of this number 

 with the number in parentheses at the head of the column shows 

 the relative abundance of the species in the formations where it 

 occurs. In the list, the species are arranged in groups in accord- 

 ance with the number of occurrences which have been noted in 

 the Cliffwood fauna; that is to say, the first three species have 

 been recognized in each of the five localities from which Cliff;- 

 wood fossils have been studied, and may, consequently, be con- 

 sidered as being among the most characteristic species of the 

 fauna, and so on down to those species which have been noted 

 from but a single locality. 



