124 Annals of the Carnegie Museum. 



Transverse diameter of P-, ■ 6 mm. 



Antero-posterior 



Transverse 



Anter-posterior 



Transverse 



" P4, approximately 10 mm. 9 



" Mx " II 



" M2 13 



" " 9 



" M:i 18 



The close relationship existing between Isectolophus and Parisec- 

 tolophiis was in reality recognized by Professor Osborn^"- and Mr. 

 Hatcher;^"^ the former included Helaletes latidens under Isectolophus, 

 and the latter expressed the opinion that this same specimen should be 

 made the type of a new genus "if it can be shown to differ generically 

 from Helaletes^ Dr. Wortman and Mr. Earl referred to this same 

 Bridger specimen as Isectolophus latidens. 



With the more complete knowledge which we now possess of the 

 characters of the type of Helaletes it is obvious ( i ) that the genus should 

 be separated from Parisectolophus as well as from Isectolophus; (2) 

 that many cranial features as well as certain characters of the teeth in 

 Helaletes agree as well, or better with those of the recent tapirs than is 

 the case with the characters with which we are acquainted in Homo- 

 galax, Parisectolophus, or Isectolophus, (3) that the generic separation 

 instituted by Wortman and Earl^"* between Ilcptodon and Ilomagalax 

 should be accepted. 



According to my view of the facts in the case Heptodon may be 

 regarded as in the ancestral line leading to Helaletes, while Ilomogalax 

 is equally clearly in the line leading to Parisectolophus and most 

 probably to Isectolophus. But we cannot seriously claim that either 

 Helaletes, Parisectolophus, or Isectolophus are direct ancestors of the 

 modern tapirs. 



Wortman, Earl, and Hatcher have questioned the view that the 

 true ancestor of the tapirs is Isectolophus}'^^ Wortman and Earl say: 

 (/. c, p. 171) "The crests of the inferior true molars are nearly cres- 

 centoid in form, which character we should not expect to find in a 



* The jaw is crushed in this region and the measurement is not rehable. 



102 '"phe Mammaha of the Uinta Formation," Trans. Amer. Philos. Soc, Vol. 

 XVI, 1889, p. 519. 



103 "Recent and Fossil Tapirs," Amer. Jour. Sci., Vol. I, 1896, p. 178. 



^oi Bull. Amer. Mus. Nat. Hist., Vol. V, 1893, pp. 178-180; I.e., Vol. \TII, 1896, 

 pp. 85-86 (Wortman). 



105 Wortman, J. L., and Earl, Charles, Bull. Amer. Mn.s\ Nat. Hist., Vol. V, 1893, 

 p. 171; Hatcher, J. B., Amer. Jour. Sci., Vol. I, 1896, p. 178. 



