XXX PKEFACE. 



John Day formations preserves the bones best for extrication. The Wliite 

 River formation of the Plains is only inferior in being a little softer, while 

 the material of the Laramie formation varies between too great hardness or 

 too great softness. The same difficulty, though in a less degree, is met with 

 in the Loup Fork beds, softness predominating, while the least favorable of 

 all for the preservation of fossils are the Puerco and Wasatch formations, 

 where concretionar}' hardness prevails. 



In all of my expeditions great care has been exercised in preserving 

 the relations in which the fossils have been found by placing marks on the 

 same and by preserving notes and drawings made on the ground. These 

 precautions are of course absolutely necessary to secure accuracy in the 

 reference of the various fragments into which a skeleton is often broken. 

 On the arrival of the collections in Philadelphia the labels on the packages 

 insure their correct classification, and the work of reuniting the broken 

 pieces commences. In many cases crania, bones, and skeletons having 

 been taken out in a moi'e or less entire condition, inclosed in rock masses, 

 much time is consumed in dressing them out with mallet and chisel. The 

 amount of labor required for the preparation of the material of the present 

 report alone, is easily seen to have been very great. I here refer to the 

 skill of my assistant, Mr. Jacob Geisman, to whom the excellent character 

 of this work is largely due. 



3. Publication of Results. — The media of publication of the results 

 of the investigations embraced in the present volume have been the fol- 

 lowing : 



1. Bulletin of the United States Geological and Geographical Survey 

 of the Territories, F. V. Hayden in charge, Washington. 



2. Annual Reports of the United States Geological and Geographical 

 Survey of the Territories, Washington. 



3. Proceedings of the American Philosophical Society, Philadelphia. 



4. Proceedings of the Academy of Natural Sciences, Philadelphia. 



5. Paleontological Bulletins. By E. D. Cope, Philadelphia. 



The last-named series consists in large part of rei)rints of papers which 

 have appeared in the serials, Nos. 3 and 4; principally in No. 3. These 

 reprints have averaged 200 copies each, but have sometimes amounted to 



