ITS NEAREST EXISTING RELATIONS. 75 



Existing Species of Equidce. 



The members of the family Equidce existing at 

 the present time upon the earth are generally con- 

 sidered to belong to one genus, that designated 

 Equus by Linnaeus. As, however, a genus is a 

 merely artificial assemblage of aUied animals estab- 

 lished for the convenience of nomenclature, zoologists 

 differ greatly among themselves as to the limits that 



J. Leidy : Extinct Vertebrate Fauna of the Western Terri- 

 tories, and other memoirs. 



E. Lydekker : Various memoirs and Catalogue of Fossil 

 Mammalia in British Museum, Part III., 1886. 



Forsyth-Major : "Beitrage zur Geschichte der fossilen 

 Pferde," 1877 (Sclnceizer paldontol. Gesellschaft, vol. iv.). 



O. C. Marsh : "Fossil Horses in America " (American Nat- 

 uralist, 1874), and other memoirs. 



A. Nehring : " Fossile Pferde aus Deutschen Diluvial- Ab- 

 lagerungen-" (Landswirtliscliaftl. Jahrbuch, 1884, Bd. xiii. 

 Heft 1, p. 81). 



Marie Pavlow : Etudes sur Vliistoire paleontologique des On- 

 gules. Moscou, i. 1887 ; ii. 1888 ; iii. 1890. 



L. Riitimeyer: "Beitrage zur Kenntniss der fossilen 

 Pferde," 1863 ; " Weitere Beitrage zur Beurtheilung der Pferde 

 der Quaternar-Epoch " (Abliand. Scliweizerisclien paldont. Ge- 

 sellscli., 1875). 



M. Schlosser : " Beitrage zur Kenntniss der Stammesge- 

 schichte der Huf thiere, und Versuch einer Systematik der Paar 

 und Unpaarhufe" (Morplwlog. Jalirb., 1886, Bd. xii., Heft 1). 



M. Wilckens : " Forschungen auf dem Gebiete der Palaon- 

 tologie der Hausthiere (Biol. Centralblat, 1889). 



J. L. Wortman : " On the Origin and Development of the 

 Existing Horses " (Kansas City Review of Science, 1882, Nos. 

 2 and 12). 



