908 THE JOURNAL OF GEOLOGY. 
The studies of Wallace have elevated island life into a distinct 
field of investigation. In the study of an island fauna, whose 
records, and even the island itself, are buried in the rocks, the 
task of interpretation becomes especially difficult. The conclu- 
sions to which one may arrive, however, equal in importance 
those reached in the study of recent island faunas. The study 
of the littoral faunas has much the same nature and importance 
as that of the islands themselves. So far as the writer is aware, 
however, there never has been published the results of a special 
study of a circum-insular fauna of palzeozoic time. 
In the detailed study of any fossil fauna the paleontologist 
must ask himself of each individual genus and species, is this an 
evolution form, or is ita migration form? Every genus or species, 
in whatever geologic or geographic position it may be found, 
falls into one of these two categories. Either its ancestors have 
lived in the same geographic area where it exists, or they lived 
in some other part of the world, and the genus or species is in 
the particular position where it is found, through migration from 
the original center of evolution. This migration may have occu- 
pied a series of generations. Very often these questions cannot 
be answered, but in most cases an answer can be found for those 
forms which give character to the fauna. 
From the nature of the case the fauna of the Chouteau 
group was composed necessarily of migration species. An area 
of land had become sea-bottom, having no preéxisting marine 
fauna, it had to be peopled, if peopled at all, by organisms which 
come in from without. This does not, however, make it neces- 
sary that the migration should have been a distant one. On a 
critical examination of the fauna it is found that the ancestry of 
the individual genera and species can be traced back to two dif- 
ferent sources. These are the middle and lower Devonian faunas 
of the East and the Devonian fauna of Europe and the West. 
Generic evidence of the origin of the littoral fauna about the Ozark 
Island. The typical Kinderhook beds were deposited nearer the shore of the main- 
land of that time and under somewhat different conditions, and it might be mislead- 
ing to use the term in this connection. It is only the circum-insular fauna as found 
in the Chouteau beds that is considered here. 
