288 E. L. Troxell — Status of Homogalax 



Aet. XXVII. — The Status of Homogalax, with Two New 

 Species; by Edward L. Troxell. 



[Contributions from the Othniel Charles Marsh Publication Fund, Peabody 

 Museum, Yale University, New Haven, Conn.] 



Homogalax Hay constitutes a genus of odd-toed animals 

 whose relationship to the early horses is both near* and 

 confusing". The older genus Systemodon Cope has been 

 broken up, part going to form this newer genus, and part, 

 including the genoholotype, being put under Hyracother- 

 ium Owen, one of the earliest of the Equidae. 



In 1875, 1 Cope made the species Orohippus tapirinus, 

 which in 1877 2 he referred to Hyracotherium; in 1881 3 he 

 made the distinct genus Systemodon for it, because he 

 concluded from a study of additional material that the 

 species showed the lack of a diastema, a new feature. 



It is necessary to disregard Cope's later descriptions 

 and figured specimens in attempting to determine what 

 Systemodon and its type, S. tapirinus, really are, and the 

 fragmentary character and limited amount of the holo- 

 type make accurate comparison impossible. Strangely 

 enough, neither the original type nor any of the later 

 referred specimens exhibit the feature on which the genus 

 was supposed to be based. 



In 1896 4 Wortman placed the species S. tapirinus again 

 under Hyracotherium, which he considered a synonym of 

 Eohippus Marsh. Hay therefore in 1899 5 proposed the 

 name Homogalax, type "S." primcevus Wortman, and 

 intended to have it include the species Si semihians Cope. 

 There is ample justification for the erection of this new 

 genus because of the imperfection of the holotype of 

 S. tapirinus and because of fundamental differences, 

 especially in the form of M 3 as judged from other mate- 

 rial; but on account of the presence of diastemata, the 

 small heel on M 3 , and for other reasons, U S." semihians 

 can not be included in Homogalax Hay. It appears, more- 

 over, that this species belongs to no known genus. 



1 E. D. Cope, Systematic catalogue of Vertebrata of the Eocene of New 

 Mexico. TJ. S. Geog. Surv. W. 100th Merid., p. 20. 



2 E. D. Cope, U. S. Geog. Surv. W. 100th Merid., 4, Palaeontology, p. 263, 

 pi. 66, figs. 12-16. 



3 E. D. Cope, Amer. Nat., 15, 1018. 



4 J. L. Wortman, Bull. Amer. Mus. Nat. Hist., vol. 8, 94-95, 1896. 

 O. P. Hay, Science, new ser., 9, 593, 1899. 



