400 memoirs of the carnegie museum. 



Earlier Investigations. 



A number of papers dealing with the subject of this memoir have from time 

 to time appeared, based upon material obtained ]\v different parties, who in the 

 past two decades have worked in western Nebraska and contiguous territory. 

 Some of these papers possess genuine value. Other papers have also appeared, 

 which indicate that the study given by their authors was hasty and of only a 

 preliminary nature, often containing mistakes, which cause more or less difficulty 

 to the student. One marked error has been the attribution of specific value to 

 certain characters of the dentition and other parts, which after a more exhaustive 

 study are clearly seen to be misleading. It is hoped that the following pages may 

 prove to be a stimulus to further study and the exercise of greater care in this 

 field of investigation. 



In earlier contributions relating to the Diceratheres published by the author 

 it has been stated that a more detailed study of the large collection obtained in the 

 Agate Spring Fossil Quarries would be forthcoming, after the process of extracting 

 the fossils from the matrix should be completed. Since that announcement much 

 work has been done. The writer having at his command material consisting of 

 the remains of some two hundred or more individuals, was induced to question the 

 validit.y of some alleged specific characters. It is hoped that the following pages 

 may supply safeguards against error in the future. \Mth only a few specimens 

 before him, a student may establish species to his own satisfaction upon characters 

 selected by him at the time, but which after more abundant material is accessible 

 to him may jirove to be invalid. 



In various publications^ there have been reported to be in the Agate Spring 

 Fossil Quarries and their immediate neighborhood no less than seven species of 

 the genus Dicer atherium, besides a new genus, Metacoenopus. At first glance it 

 might appear that the characters relied upon by the authors in establishing the 

 different forms are valid, but after a more intensive study it is found that some 

 species must be abandoned, and others must be regarded as doubtful. The result 

 of our recent investigations proves that in this case we must either condense the 

 number of proposed species, or establish an infinite number of additional new forms. 

 The latter course would be eminently unscientific, though justifiable if we accept 

 as valid the characters employed and relied upon in discriminating the various 



1 Loomis, F. B., Amer. Jour. Sci., Vol. XXVI, 1908, p. 51-64. Cook, Harold J., Amer. Naturalist, 

 Vol. XLII, 1908, p. 543-545; Nebraska Geol. Surv., Vol. Ill, 1908, p. 245-247. Barbour, E. H., Science, 

 N. S., Vol. XXIV, Dec. 14, 1906, p. 780-781. Peterson, 0. A., Science, N. S., Vol. XXIV, Aug. 31, 1906. 

 p. 282-283. 



