416 



TITAJSrOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



The internal valleys are more prominent and con- 

 spicuous, and the hypoconulid is reduplicate. In the 

 more worn m2 of the same specimen (ap. 43 mm., tr. 

 25) these internal valley folds have been worn away, 

 and the same is true of the still smaller mj (ap. 35 

 mm., tr. 20). The external cingulum is more sharply 

 accented in some specimens (as in Am. Mus. 1855) 

 than in others. 



Jaw of DolichorTiinus hyognathus. — The somewhat 

 fractured and crushed type jaw (Princeton Mus. 

 10273) presents the distinctively long and shallow 

 ramus and shallow sloping symphysis that are char- 

 acteristic of this species. (See fig. 353.) The measure- 

 ments given below serve to determine the variations 

 due to age, to sex, and in a measure to the progressive 

 evolution of this type. 



Measurements oj Dolichorhinus hyognathus, in millimeters 



Washakie B 2 



Am. Mus. 

 13164, V 



Princeton 

 Mus. 10273, 

 <? (type) 



Am. Mus. 

 1862, old ? 



Am. Mus. 

 1856, 9 



Condyle to incisive border 



Depth, condyle to angle 



Depth, ramus behind pz 



Depth, ramus behind m2 



Depth, ramus behind ma 



Length of symphysis 



Least width of chin 



Free height of coronoid 



Thickness of ramus below m2 



Vertical thickness of symphysis posteriori}'. 



Canine to ms 



Pi-ms 



Pj-ms 



Mi-ma 



Transverse diameter ofms 



448 



+ 135 



58 



69 



74 



109 

 59 



445 



65 

 79 

 95 

 115 

 57 



65 

 75 

 95 

 114 

 62 



■112 

 61 



102 

 55 

 65 



32 



268 

 230 

 213 

 138 

 26 



■300 

 "246 

 '218 

 •137 



27 



26 



37 

 276 

 233 

 210 

 142? 



27 

 270 

 223 

 194 

 127 



(?) 



430 



■148 



54 



60 



79 



117 

 55 



29 

 30 



274 

 238 

 207 

 138 

 27 



We observe that the specimen from Washakie B 

 (Am. Mus. 13164), a female, is practically similar in 

 its measurements to the females found in Uinta B 2. 

 (Am. Mus. 1852 may belong to the species D. longi- 

 ceps.) 



The most perfectly preserved rami are those of the 

 females Am. Mus. 13164 (Washakie B) and 1856, from 

 which Figure 353 B is taken. 



The symphysis is greatly elongated (114 mm.) in the 

 type of D. hyognathus. The ramus increases very 

 gradually in depth from 50 millimeters in front of p? 

 to 85 in front of ms, being of moderate thickness 

 (26 mm.) In the female jaw Am. Mus. 13164 (from 

 Washakie B) the angle is produced moderately down- 

 ward and backward, the condyle not being so greatly 

 raised (138 mm.) above the angle as in the brachy- 

 cephalic types. The most distinctive feature is the 

 coronoid, which is produced backward so as to over- 

 hang both condyle and angle. 



Dolichorhinus heterodon Douglass 

 Plate LXXIII; text figures 133, 134, 343 



[For original description and type references see p. 187] 



Type locality and geologic horizon. — Uinta Basin, 

 Utah; horizon Uinta B 2 or C 1 (Douglass). 



Specific characters. — A small, aberrant form, pos- 

 sibly related to D. intermedius; distinguished by some- 



what larger size, p'-m^ 189 millimeters, faciocephalic 

 index 50. Secondary palate above level of primary 

 palate; large occipital condyles; premolars and molars 

 with heavy internal and external cingula; a distinct 

 mesostyle and a prominent parastyle on p*; premolar 

 ectolophs very oblique. Agreeing with D. intermedius 

 in general skull and tooth characters and especially in 

 the marked anteroposterior convexity of the parietal 

 vertex. 



Materials. — Represented by the type specimen only, 

 in the Carnegie Museum (No. 2340). As shown by 

 the accompanying measurements this type represents 

 an animal distinctly smaller than D. hyognathus and 

 closely allied to D. intermedius, of which it may be a 

 somewhat more progressive successor. 



Among its primitive features is the elevation of the 

 secondary palate above the plane of the primary 

 palate. The secondary palate is present in the type 

 specimen but has not yet grown do^vnward near the 

 horizontal plane of the primary palate as in D. cornutus. 

 Among its progressive features distinguishing it from 

 D. intermedius are the heavier internal and external 

 cingula of the upper premolars and molars, the well- 

 developed mesostyle on p*, and the prominent para- 

 style on p', p*. A very rudimentary mesostyle is 

 observed on p^ which is a rare feature among titano- 

 theres, as ordinarily mesostyles are not developed in 

 the premolars. 



