16 OSBORN. 



kingen and Lissieu that they are composite faunae, contain- 

 ing upper Eocene forms mingled with the middle Eocene 

 forms, therefore, they 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 PalcEotapirus buxovillamis ('88, p. 179, pi. XIX, fig. 

 4), which certainly belong not to the Tapir idee but to the 

 Helaletinee, a sub-family of LopJdodontidee. On the other hand, 

 the upper molar and the lower jaw^ assigned to HyracJiyzis inter- 

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

 Argenton resemble the HelaletiiieE in a Wasatch or Heptodon 

 stage of development because 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 BeaiicJiainp, marine (15 

 metres) is succeeded by the partly lacustrine Calcaire de Saint 

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

 considered parallel. 



From the Gr(:s de Cesseras a few mammals are recorded. 

 The Cesserasietis antiqiins (Filhol '88, p. 182, pi. XIX, fig. 3) 

 type is a small lophiodont jaw with molar teeth which resemble 

 those of Helaletes 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 Lophiodon cesser as- 

 siciiin Filhol {L. oceitaniejtm, Gervais) is judging by Gervais' 

 figures (pi. 18, fig. 7), one of the Equidee 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 w^hich it contains. 



The writer is chiefly indebted to Professor Albert Gaudry for 

 the arrangement of the lower Eocene in the accompanying 

 'Third Trial Sheet.' 



