126 Annals of the Carnegie Museum. 



acters of the upper dentition, of which we have just spoken, taking no 

 account of the limb and foot structure of the Eocene pseudotapirs, 

 we find difificulty in accepting as natural such a fluctuation as we 

 must admit to have occurred were we to place Isectolophns or Parisec- 

 tolophus in the direct line of ancestry to Protapirus. These Eocene 

 tapirs of North x^inerica, if they continued into the Oligocene, had as 

 their successors, not Protapirus, but some form contemporaneous 

 with the genus Colodou. The true Eocene ancestors of the Oligocene 

 and recent tapirs cannot logically be said to be represented by the 

 remains heretofore found in the Eocene of North America. 



Isectolophns, Parisectolophus, and possibly Schizolophodon^'^'' appear 

 to form a second independent line of Eocene tapirs paralleling that 

 represented by Heptodon, Helaletes, and Colodou. 



Since we now know the upper dentition of Isectolophns better than 

 heretofore, it is obvious that Professor Osborn's inclination to refer 

 Riitimeyer's Lophiodon annectens to Isectolophns,^"^ and the acceptance 

 of this reference by Trouessart^"^ and others, cannot now consistently 

 be continued. Riitimeyer's illustrations '^° indicate different outlines 

 and configurations of the grinding surfaces, besides greater height 

 of the cross-crests and a greater amount of cement in the different ele- 

 ments of which the teeth are composed; in the latter respect apparently 

 more rhinocerotic than is the case in Isectolophns. The name Lep- 

 tolophiodon annectens (Riitimeyer) might be proposed for this European 

 form, which must in any event be excluded from the American genus. 

 Furthermore, it is questionable whether this European genus should 

 even be included in the Isectolophincc. 



"^ The imperfect cross-crests of the molars of Schizolophodon suggest a conser- 

 vative type, which recalls the condition in Homogalax or Eohippus, and may belong 

 in a separate subfamily. 



^°^ Amer. Naturalist, Vol. XXVI, 1892, p. 763. 



1°^ Catalogus Mammalium, p. 765 (riithneyeri). 



^^° Abhand. Schw. Pal. Ges., 1891, p. 26, PI. I, Figs. ii-i3- Note: Specimens 

 represented by Fig. 12 in Rutimej^er's illustrations (PI. I) are perhaps most sug- 

 gestive of the American genus Isectolophns, but according to the illustrations, the 

 cross-crests are more curved, the ectoloph thicker, and the teeth contain more 

 cement. 



