J. B. Hatcher — Recent and Fossil Tapirs. 169 



Measurements. 



Greatest length of jaw 220 mm 



Depth of jaw below pm. 2 31 



" " " ra. 3 40 



Length of diastema 30 



Length of premolar-molar series 98 



" molar series 55 



Colodon (Marsh).* 



The present genus is distinguished from Protapirus, which 

 it most resembles, by the presence of a fifth cusp on the last 

 inferior molar ; by the reduction of the number of lower incis- 

 ors to two on either side ; by the more molariform superior 

 premolars and by the shape of the postero-external cone of the 

 superior molars, which in the present genus is concave on its 

 external surface. The inferior premolars of Colodon are dis- 

 tinct from those of Protapirus, in that the postero-external 

 cone is always connected with the antero-external by a low 

 ridge. The second inferior premolar is proportionately very 

 much shorter in Colodon than in Protapirus. 



Although remains of Colodon are rarely found, yet five 

 species have already been proposed, viz : C. (Lophiodort) occi- 

 dentalis (Leidy)f, founded on a last inferior molar; C. luxatus 

 (Marsh);):, founded on a lower jaw in which pm. 2 is absent ; 

 C. dakoiensis (O. and W.)§, founded on a complete superior 

 dentition, with a portion of an inferior dentition and sup. pm. 

 4, from another individual as a collateral type ; C. procuspida- 

 tus (O. and W.),|| founded on a superior dentition from one 

 side in which m. 3 is wanting and pm. 1 is injured, and C. 

 (Jlesohippus) loncjipes (O. and W.),^f founded on a hind foot 

 now provisionally referred to Colodon although first described 

 as Mesohippus longipes. Prof. Marsh's type of C. luxatus 

 agrees, in size and all essential characters, with Leidy's occi- 

 dentalis in so far as we are able to determine those of the 

 latter, from Leidy's description and figures, and both appar- 

 ently belong to the same species. 



Osborn and Wortman remark, in closing their description of 

 C. procuspidatus, that "the only means at present known of 

 distinguishing C. procuspidatus from C. occidental (spelling 

 theirs) is by the smaller size and generally less robust charac- 

 ter of the latter." They give the horizon as the Metamyno- 



* See this Journal, June, 1890, p. 524, and Nov., 1893, p. 411. 



f See Extinct Mam. Fauna, Dak. and Neb., p. 239. 



% Loc. eit. 



§ See Bull. Am. Mus. Nat Hist., vol. vii, p. 3G2. 



|| See Bull. Am. Mus. Nat. Hist., vol. vii, p. 364. 



1" See Bull. Am. Mus. Nat. Hist., vol. vii, p. 366, and vol. vi, p. 214. 



