438 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



opment of the antero-internal angle in the species under con- 

 sideration. In the type of Diplacodon datum p' is lost, while 

 the external portion of p^ is broken off. In the present species 

 the deuterooone of p^ is less ridgelike than in D. elatum, the 

 two interal tubercles being somewhat better indicated and the 

 ridge between them distinctly less developed. P' is more 

 quadrate in outline than the preceding tooth and has two dis- 

 tinct internal tubercles on the crown, which are separated by a 

 shallow groove, while in Diplacodon elatum these tubercles are 

 united into a solid internal ridge, revealing a distinct differen- 

 tiation from what is seen in the present species [compare PI. 

 LXXXll. On the other hand, p' both in the type we are 

 describing and in D. elatum are similar, there being two internal 

 tubercles, deutero- and tetartocones, the former considerably 

 the larger.^" The more important differences in the dentition 

 of the two forms, so far as they can now be compared, seem to 

 be in the proportion of the canines, the difference in the length 

 of the premolar series, and the detailed structure of p'. The 

 greater length of the premolar series is naturally to be expected 

 in a form from a lower geological level. 



The detailed characters of the molar series of the genera here 

 compared present no differences of importance. The two Uinta 

 forms agree in the obscure or feeble development of the cusp- 

 like elevations on the anterior face of the molars near the inner 

 angle, more conspicuously developed in Titanotherium. At the 

 postero-internal angle of the cingulum of m' in the Oligocene 



Figure 367. — Two upper molars of Eotitano- 

 therium {" Diploceras") osborni Peterson 



Crown view. One-half natural size. Carnegie IVIus. 2860a. 

 These isolated teeth were found with the paratype, Carnegie 

 Mus. 2S60; Duchesne River near Myton, Uinta County, 

 Utah.; Uinta B 2. 



forms there is sometimes a distinct tubercle, which is indicated 

 in the Uinta forms by only a slight swelling of the cingulum. 



In proportion the inferior incisor dentition is further in ad- 

 vance of the canine than in P. emarginatum. Ii and i2 are repre- 

 sented only by a portion of their roots buried in the symphysis. 

 I3 has a very prominent cingulum posteriorly. Notwithstand- 

 ing the much smaller size of the specimen, its crown has very 

 nearly the same diameter as in P. emarginatum, which would 

 indicate that the inferior incisors were possibly larger in propor- 

 tion and more nearly equal in size. The crown of the canine 

 is injured, but its diameters appear to be equal to those in the 

 superior series, though relatively smaller than in P. emar- 

 ginatum. Pi has a single root and a simple conical crown, 

 which has not received any wear, due to its somewhat inferior 

 position. Pj is submolariform and in its general characters 

 does not differ from the same tooth in P. emarginatum. P3 is 

 quite molariform, while P4 has a complete molar pattern. 



There is no difference in the general features of the lower 

 molars in the two genera here compared, and in turn the molars 

 of Diplacodon are on the whole quite similar in their detailed 

 structure to those of the Oligocene genus. 



•» In No. 2858, the paratype, there is only one internal tubercle, the deuterocone 

 which may by some be regarded as of sufficient importance to constitute a specific 

 difference. For the present I prefer to regard this character as possibly representing 

 a reversion. 



The proportion of the alveolar border occupied by the lower 

 premolars of this species is in accord with the upper series — 

 that is, of a greater anteroposterior diameter than in P. emar- 

 ginatum and D. elalum.^^ Judging from the type (lower jaw) 

 of Protitanotherium superbum Osborn, recently described,'^ that 

 species also has the same proportion of the molar-premolar 

 series as the two latter, while Telmatherium? altidens of the 

 same publication has a longer premolar series and more nearly 

 agrees with the present genus. 



Measurements, in millimeters 



Length of superior incisor series 



1', anteroposterior diameter 



1', transverse diameter 



I^, anteroposterior diameter 



I^, transverse diameter 



I' , anteroposterior diameter 



1', transverse diameter 



Canine, anteroposterior diameter at the base. 



Canine, transverse diameter at the base 



Length of molar-premolar series 



Length of superior premolar series 



P', anteroposterior diameter 



P', transverse diameter 



P^, anteroposterior diameter 



P^, transverse diameter 



P', anteroposterior diameter 



P^, transverse diameter 



P*, anteroposterior diameter 



P*, transverse diameter 



Extent of superior molar series 



M', anteroposterior diameter 



M', transverse diameter 



M^, anteroposterior diameter 



M^, transverse diameter 



M', anteroposterior diameter 



M', transverse diameter 



I3, anteroposterior diameter 



I3, transverse diameter 



Canine, anteroposterior diameter, approxi- 

 mately 



Canine, transverse diameter, approximately 



Length of inferior molar-premolar series 



Length of inferior premolar series 



Length of inferior molar series 



Pi, anteroposterior diameter 



Pi, transverse diameter 



P2, anteroposterior diameter 



P2, transverse diameter 



P3, anteroposterior diameter 



P3, transverse diameter 



P4, anteroposterior diameter 



P4, transverse diameter 



Ml, anteroposterior diameter 



Ml, transverse diameter 



M2, anteroposterior diameter 



M2, transverse diameter 



M3, anteroposterior diameter 



M3, transverse diameter 



No. 2859 No 



34 

 11 

 10 

 12 

 12 

 15 

 14 

 19 

 18 

 246 

 101 

 19 

 12 

 22 

 25 

 30 

 31 

 33 

 38 

 ■146 

 38 

 45 

 52 

 54 

 67 

 51 

 14 

 12 



17 

 14 



255 

 94 



160 

 14 

 10 

 24 

 14 

 28 

 18 

 29 

 20 

 38 

 26 

 49 

 30 

 78 

 32 



" Professor IMarsh's measurement of the molar series of the type of D. elatum is 



31 In remeasuring the molar series of Prof. IMarsh's type of Diplacodon elatum it 

 would seem that he was in error in regard to the measurement, which should read 

 167 instead of 152 millimeters. 



3! Osborn, H. F., New and little-known titanotheres from the Eocene and Ohgo- 

 cene: Am. Mus. Bull., vol. 24, p. 615, 1908. 



