266 Annals of the Carnegie Museum. 



comparatively short geologic time in a gi\en locality. From the study 

 of the changed lithological features, of the strata, together with 

 the changes of the faunae of different horizons, in certain localities, 

 one is able to form a mental picture, of possible causes for the varied 

 changes in structure. It is possible to imagine a locality so altered 

 that a certain portion of its inhabitants which were capable of modifi- 

 cations, did modify in order to fit themselves to the requirements of 

 their rapidly changing environment; others migrated, or perished; their 

 places being filled by different forms from other places. In turn the 

 introduced forms would become greatly multiplied on account of con- 

 ditions which had become especially favorable to them. Or, on the 

 other hand, the immigrants found the new habitat less desirable and 

 only lingered awhile until they reached extinction. 



After a careful comparison of the above described type with other 

 Miocene camels, I find that it most nearly agrees with Oxydactylus, 

 though it is with some reluctance that it has been referred to that 

 genus on account of its long head and short neck, which are certainly 

 deep-seated characters pointing to an earlier origin than the compara- 

 tively brief time of the deposition of the Lower and Upper Harrison 

 beds. I assume, therefore, that the line was perhaps already estab- 

 lished in the late Oligocene and that the different forms paralleled each 

 other. The discovery of complete limbs in connection with the skull 

 and vertebrae of this species would be a most welcome help to com- 

 pletely determine its phylogenetic position. 



