204 PROCEEDINGS OF THE ACADEMY OF [1893. 



phodont, while the Mexican species is bunolophodont. The various 

 characters just mentioned also distinguish M. praecursor from 

 T. shepardii. There is no evidence that the Mexican species 

 possesses an enamel band on the superior incisors. My assertion to 

 this effect was based on a specimen which presents this character 

 which is preserved in the Esquela das Minas of Mexico. This 

 specimen came from Tehuichila, in the State of Vera Cruz, from a 

 formation which I subsequently determined to be of Loup Fork 

 age, so that the identity of the species with that found in the Equus 

 beds of the valley of Mexico is highly improbable. I therefore 

 refer the latter to the genus Mastodon under the specific name of 

 M. oligobunis Cope. It differs from Dibelodon tropicus in the 

 smaller number of cross-crests of the last molar, and their greater 

 simplicity, since they are not divided at all, and the external halves 

 of the first and second only have anterior, and posterior buttresses, 

 in some of the individuals at least. 3 



Measurements of T. shepardii. 



J r M M ^ 



Length of right ramus and symphysis 730 



Length of right ramus to symphysis 515 



Depth of ramus at posterior end of M. iii 135 



Deptfrof ramus at anterior end of M. ii 175 



Width across both rami at posterior end of M. iii 420 



Width of right ramus at posterior end of M. iii 140 



Width of both rami at base of symphysis 214 



Width of spout at proximal end 65 



Width of distal extremity of symphysis 120 



Length of spout 215 



_. „ ,, ..(anteroposterior 125 



Diameters of M. n \ , .,,, __ 



(. transverse at middle 75 



_. „ , , ... (anteroposterior 164 



DiametersotM.ini, r .„, __ 



(.transverse at middle 75 



Diameters of right symphyseal tusk j vertlcal 68 



(transverse 27 



Diameters left symphyseal alveolus j vertical 78 



(.transverse 45 



3 A figure of this tooth is given by Felix in Paleontographica, Vol. xxxvii, 

 pi. 30,1891. 



