16 OSBORN. 



kingen and Lissieu that they are composite faunae, contain- 

 ing upper Eocene forms mingled with the middle Eocene 

 forms, therefore, the)' cannot be cited at all as proofs of syn- 

 chronism. Similar Helaletes-like teeth are described by Filhol 

 from Buchsweiler, Alsace, namely the type 3d and 4th premo- 

 lars of his Palaotapims buxovillamis ('88, p. 179, pi. XIX, fig. 

 4), which certainly belong not to the Tapiridee but to the 

 HelaletincB, a sub-family of LopJiiodoutidic. On the other hand, 

 the upper molar and the lower jaw assigned to Hyraeliyus inter- 

 Diedins (Filhol '88, p. 114, pi. XXX, figs. 8 and 6) from 

 Argenton resemble the Hclaletince in a Wasatch or Heptodoii 

 stage of development becau.se they are small and simple. 



7. Middle Eocene, Bartonien, apparently Equivalent to the 

 Lower Bridger 



This substage receives its name from the Barton Clays of 

 England (100 metres). The Sables de Beaiichavip, marine (15 

 metres) is succeeded by the partly lacustrine Calcaire de Saint 

 Oiiei! with which the fresh water Gres de Cesseras (Herault) are 

 considered parallel. 



From the Gres de Cesseras a few mammals are recorded. 

 The Cesserasietis antiques {Yi'lwo'l'^^, p. 182, pi. XIX, fig. 3) 

 type is a small lophiodont jaw with molar teeth which resemble 

 those of Helaletcs of the Bridger except in the extreme sim- 

 plicity of the supposed 4th premolar. 



If Filhol's identification and description is correct no com- 

 parison can be made with our Bridger Helaletes which has 

 a partly compound fourth premolar. The LopJnodon ccsseras- 

 sicniii Filhol (Z. oeeitaineum, Gervais) is judging by Gervais' 

 figures (pi. 18, fig. 7), one of the Eqiiidcc in a Bridger stage 

 of development. 



The American parallel of the Bartonien is probably Lower 

 Bridger but it cannot be determined until we secure a more ex- 

 act knowledge of the state of molar and premolar evolution of 

 the few ungulate fossils which it contains. 



The writer is chiefly indebted to Professor Albert Gaudry for 

 the arrangement of the lower Eocene in the accompanying 

 'Third Trial Sheet.' 



