IV 



hut to complf^te (lie worU in varimis groups in cases wlipre specialists are 

 jiicparfd to do so. 



Other monographs are in an advanced state of" preparation, based on 

 the collcictions o(" tlie Survey, whicli will he printed as soon as they can he 

 rendered more complete Iiy fartiier investigations in the field. 

 Very respectfully, your obedient servant, 



F. V. haydp:n. 



United States Geologist. 

 lion. Z. Chandler, 



Secretartj of the Interior. 



