64 GEOLOGICAL SURVEY OF TEXAS. 



Measurements. 



TiBngth of symphysis mandibuli 120 



Length from M. ii to eud of symphysis 222 



Diameters of M. FT \ anteroposterior 114 



( transverse at middle 65 



Diameters of M. JIT. i anteroposterior 190 



( transverse at front 70 



Elevation of M. liT. at front (little worn) 40 



Depth of ramus at front of M. UT. 190 



Depth of ramus at posterior end of symphysis 120 



The first true molar found alone is half worn. It presents a narrow 

 anterior cingulum and a prominent heel of several tubercles. The last 

 premolar from Paloduro is unworn. The bilobation of the internal halves 

 of the crests is very strongly marked, as is also the trilobate character of 

 the external halves. The posterior inner lobe of the trefoil is lower than 

 the anterior inner. An anterior cingulum and narrow heel. 



Measurements. 



Mm. 



Length of M. L 91 



Width of same at middle 58 



Length of P. m. L. 94 



Width at middle 58 



Elevation of anterior crest 49 



The anterior molars agree with the posterior molars in their diversity 

 from the corresponding teeth of the D. humboldtii from the same region. 

 But one side of the crown presents trefoils, and the lobes in the anterior 

 molar and last premolar do not display the additional plications seen in 

 that species. This difference is most striking, and emphasizes that found 

 in the true molar, since in the anterior crest of the last true molar they 

 are not so pronounced. 



This species adds another element to the tropical American contingent 

 of the Blanco fauna. Its southern range extends to Peru, if, as I sus- 

 pect, a ramus of the mandible, with the last molar from that country, 

 presented by Dr. Coates to the Academy of Natural Sciences of Philadel- 

 phia, pertains to it. 



DIBELODON PRECURSOR, CopC. 



Sp. nov. Plates XVIII, XIX. 



A hundred yards from the locality which produced the specimens of 

 mastodons already described, Mr. Duncan Cummins found a posterior 

 molar of another species in the side of the bluff from which I had exca- 

 vated the jaw of the Pliauchenia spatula. This molar tooth has lost its 

 anterior cross-crest, but is otherwise perfect, and is unworn. 



