322 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 8 



it will help greatly to lessen the confusion that arises when formations 

 are encountered, and the scattered or unavailable literature is not 

 at hand for aid in placing them in proper position in the section. 



Efforts should be gradually made to correlate more closely the 

 faunas occurring under different ecologic conditions but of contem- 

 poraneous age. The faunas of shallow littoral waters are usually 

 very different from those of even moderately deeper water. Where 

 beds cannot be traced over long distances, and changes in sediments 

 occur, due to differences in depth, correlation is difficult. The 

 student of palececology should find studies along this line fascinating 

 to himself and the results very useful to the geologist and stratig- 

 rapher. It is very probable that some of the present-day contro- 

 versies over the relative ages of different beds might be easily and 

 definitely settled if such ecologic factors were better known. There 

 are examples in our sections where fossils of one group of animals 

 seem to indicate a different relationship than those shown by other 

 animal groups. A closer cooperation of workers on different zoologic 

 divisions will probably show that one group was more rapidly changing 

 under the particular environmental conditions, and that, under 

 certain conditions, greater weight should be given to one group than 

 to another. Very much is to be learned by the paleontologist of the 

 future along these and related lines. 



In the realm of economic geology, paleontology, especially micro- 

 paleontology, has demonstrated great usefulness. Particularly in 

 petroleum discovery and recovery, the microfossils have been of 

 inestimable value. Their usefulness has been due to their immense 

 numbers, especially the foraminifera, and the fact that their small 

 size allows them to be recovered unharmed by the process of drilling. 

 The rapid changes in characters in the foraminifera and the large 

 number of species usually present in a relatively small sample make 

 them especially valuable for correlation purposes. The use of micro- 

 fossils for correlation is already widespread in the search for oil. 

 Shallow core drilling to determine subsurface structures is now used to 

 a great extent. Where no surface outcrops allow the field geologist 

 a clue to what is beneath, this method opens up a relatively inex- 

 pensive method of revealing subsurface structures. 



The value of such work depends upon the extent to which the micro- 

 faunas of the beds of the section are known. Particularly where sub- 

 surface faulting must be accurately located as in some of the areas of 

 Texas, the point of change of faunas must be recognized within very 

 narrow limits. Keen discrimination and an intimate knowledge of the 

 various faunas are necessary for success in this rapidly growing field. 

 A large part of this information, and the material upon which it is 

 based, is not generally available, but is kept in the files of different 

 companies who are operating in these fields. Such information should 



