

*>^-~. ■"■. u 





THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES. J 



Aet. XIX. — Principal Characters of the Protoceratidce ; by 

 O. C. Marsh. Part I. (With Plates II- VII.) 



The genus Protoceras, described by the writer in 1891, 

 from the Miocene of South Dakota, is now known to include 

 some of the most interesting extinct mammals yet discovered. 

 It likewise represents a distinct family, and thus deserves care- 

 ful investigation and description.* Before this discovery, no 

 horned artiodactyles were known to have lived during Miocene 

 time, and Protoceras is thus the earliest one described. The 

 type specimen, moreover, had a pair of horn -cores on the parie- 

 tals, and not on the frontals as in modern forms of this group. 

 The animal was apparently a true ruminant, nearly as large as 

 a sheep, but of more delicate proportions. 



The first skull found, the type specimen of the genus Proto- 

 ceras, belonged to a female, as later discoveries demonstrated. 

 The skull of the male proved still more remarkable, and espe- 

 cially resembles the male skull of the Eocene Dinocerata in 

 having several pairs of horn-cores or protuberances upon the 

 head, a feature hitherto unknown among the Artiodactyla. 

 It is an interesting fact, moreover, that one pair of these horn- 

 cores of Protoceras is on the maxillaries, as in Dmoceras, 

 while the posterior pair, as in that genus, is on the parietals. 



* This Journal, vol. xli, p. 81, January, 1891; and also, vol. xlvi, p. 407, 

 November, 1893. 



Am. Jour. Sci.— Fourth Series, Vol. IY, No. 21.— Sept., 1897. 

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