1917] 



Merriam: Pliocene Mammalian Faunas 



441 



with the Snake Creek, consider that modernization is more apparent 

 in the latter. The Republican River canid fauna contains only ad- 

 vanced forms of the Aelurodon or Dinocyon type. The Equidae in- 

 clude Hypohippus, Protokippus, and Neohippariou. Two oreodonts, 

 Merycochoerus and Merychyus, are present with camels of the genera 

 Procamelus and Pliauchenia. Dromomeryx and Blast omeryx are not 

 represented. Considering that the two areas discussed are widely 

 separated geographically, it would seem to the writer that the Repub- 

 lican River is not far from the stage of faunal evolution shown by 

 the Ricardo. If the Ricardo is younger than the Snake Creek, the 

 judgment of Matthew and Cook, suggesting the situation of the 

 Republican River earlier rather than later than the Snake Creek, 

 necessitates placing the Republican River somewhat below the Ricardo. 



Relationship between the fauna of the Ricardo and that of the 

 Alachua beds of Florida is suggested especially by similarity of the 

 Hipparion species. The American forms most resembling the Ricardo 

 hipparions are PL. plicatile and H. ingenuum of the Alachua beds and 

 H. venustum from Ashley River, South Carolina. This resemblance 

 may be purely incidental, but possibly indicates a close genetic rela- 

 tionship. J. W. Gidley 20 has suggested that the Florida hipparions 

 are like those of the true Old World Hipparion type with round pro- 

 tocone. It is possible that the Alachua and Ricardo Hipparion forms 

 represent some of the oldest members of this group in America, these 

 species having survived in the southeast and southwest corners of the 

 continent after the forms with round protocone had disappeared in 

 the middle regions of the continent. 



As has been known, there is a marked resemblance between the 

 Alachua fauna and the life of the Republican River and Snake Creek 

 stages. The Alachua appears more advanced than the Republican 

 River and approaches the Snake Creek more closely in the important 

 Hipparion elements. The presence of both Teleoceras and Apkelops 

 in the Alachua indicates affinities with the Miocene. The recently de- 

 scribed Mammut progenium and Agriotkerium (Hyaenarctos) indi- 

 cate with considerable definiteness the Pliocene rather than Miocene 

 aspect of the Alachua. 



-<> Gidley, J. W., Eevision of the Miocene and Pliocene Equidae of North 

 America, Bull. Amer. Mus. Nat. Hist., vol. 23, pp. 905-906, 1907. 



