PETERSON: THE AMERICAN DICERATHERES. 



413 



having a prominent shoulder at the base on their inner side. . . . Diastema long; 

 ascending ramus vertical, flat in front. Depth of ramus at last molar .065; length 

 of crown of canine [= lateral incisor] .027; width of do. at the base .024." 



This type specimen, now in the Cope collection of the American Museum of 

 Natural History, has recently been studied by the writer. After a comparison 

 with fragments of the lower jaw associated with a skull (No. 10,005) of Diceratherium 

 armatum in the Yale Museum I think it possible that this specimen may pertain 

 to that species. The thick and rather shallow ramus of Cope's type is character- 

 istic of D. armatum. The symphysis is similarly long and heavy, the mental 

 foramen is below Pi, as in the latter species, and the comparative measurements 

 of the two specimens agree fairly well. The question of the relationship of these 

 two species cannot, however, be entirely satisfactorily settled until more complete 

 material of the John Day forms is obtained. 



Additional Measurements of Type of D. truquianum Cope. 



Antero-posterior diameter of crown of median incisor 6 mm. 



Transverse " " " " " " 8 " 



Height " " " " " 6J " 



" " " lateral " 26| " 



(( (( a !• (( 90 it 



'' " " M^ 44 " 



" " M^ 46 " 



Transverse 



Antero-posterior 



Transverse 



Anterior-posterior 



Transverse 



Diceratherium petersoni Loomis^'' incertoe sedis. 

 Type. — First and second molars of left side. Amherst Museum, No. 1583. 

 Horizon. — Miocene. 

 Locality. — Agate Spring Fossil Quarries (quarry A) Sioux County, Nebraska. 



Fig. 9. Diceratherium petersoni lioomii^. M- and AP left side. No. 1.58.3, Coll. Amherst Museum. X |. 



After Loomis. 



In the extensive collection from the Agate Spring Quarries and neighborhood 

 now in the Carnegie Museum, there are not found any teeth or other remains 



'^ Amer. ,Jour. Sci., Vol. XXVI, July, 1908, p. .57, Fig. 7. Cook, Harold J., Neb. Geol. Surv., 

 Vol. VII, Aug., 1912, p. 40. 



