OSBORN AND MATTHEW, GEOLOGICAL CORRELATION 
43 
and critically considered for each typical vertebrate fauna. These faunal 
lists may then be published, as reports of progress, without committing 
individuals or the committee to decisions upon the wider questions of corre¬ 
lation. They will serve rather as summary statements of the evidence 
available. These broader correlations can then be taken up by sub-com¬ 
mittees composed of authorities upon vertebrata, invertebrata and plants, 
and the final decisions made by comparison and criticism of the evidence 
from these groups and upon such other evidence as may appear pertinent. 
Decisions of sub-committees, reviewed and approved by the committee as a 
whole, will then serve for a broad standardization. 
The first necessary preliminary is to get the data together in the following 
form: 
1. Lists of typical and well-known faunae, strictly arranged by formations 
and horizons or by geological distribution. These should include, as 
far as practicable, the character and location of type, character of re¬ 
ferred specimens, etc., in order to give some idea of how much is known 
of the species and its consequent value in correlation. Genera and 
species known from complete and abundant material are naturally of 
much more value in correlation than those reported from scales, teeth 
or other fragments. 
2. Critical observations upon the importance of the species or genera in 
correlation; their relations to others occurring in other typical faunae; 
first or last appearance of genera and families; abundance of the species 
or genus; range, time and direction of migration, and any other data 
of value in this connection. 
3. Sketch geological sections of type localities showing the level of occur¬ 
rence of the fossils and relations of overlying and underlying formations. 
Sketch maps showing the location and extent of the formations. 
4. Principal literature, chief scientific collectors who have worked in the 
field, with the date of their work, estimate of its probable accuracy and 
possible sources of error in correlation. 
5. Geographic and geologic conditions, environment and phase repre¬ 
sented by the fauna as a whole. 
Dr. Matthew has in preparation lists of the American faunae which will 
be submitted to American members of the committee for critical observations 
and sketch sections. Similar data are desired for European and foreign 
typical faunae. These data, when compiled, will be published from time 
to time as reports of progress, and the final results will be based upon con¬ 
sideration and correlation of these reports. 
