364 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



P'-m^ 176-186+ millimeters; postcanine diastema 

 short; i^ much larger than i^; p" with deuterocone and 

 tritocone poorly developed; p"* (ap. by tr.), 19 by 

 26 to 22 by 29 millimeters; m\ 28 by 29 to 32 by 33; 

 m^ 35 by 37 to 41 by 40; m^, 36 by 39 to 39 by 43. 



2. M.washakiensis: Level, Washakie A, upper part. 

 Slvull somewhat larger (basilar length in supposed 

 female 490 mm., estimated). Face relatively short; 

 zygomata moderate; horn swelling inconspicuous (? 9 ). 

 P'-m', 200 milhmeters (estimated); p^ with deutero- 

 cone somewhat better developed; p* (ap. by tr.), 23 by 



29 millimeters; m\ 35 by 38; m^ 41 by 43; m', 39 

 by 42. 



3. M. uintensis: Level, Uinta C, lower part. Skull 

 larger (basilar length not known). Face relatively 

 long; female horn swelUng (?) absent; zygomata not 

 stout, in inferior view forming a marked angle in front 

 of the glenoid surface. Postcanine diastema long; 

 disparity of i^ over i^ less marked; p'-m', 240 milli- 

 meters; p^ with deuterocone slightly and tritocone 

 markedly more advanced; p* (ap. by tr.), 26 by 32 

 millimeters; m', 40 by 38; m^, 52 by 46; m', 45 by 50. 



Range in size of Manteoceras manteoceras and two successive stages oj increase in size, in millimeters 



" Estimated. * Crushed. 



Numbers at heads of columns are those of the American Museum except the last (2388), which is of the Carnegie Museum. 

 The geologic horizon and other facts concerning the specimens are given below: 



12194. Intermediate molar proportions. Bridger C 2. 



12678. Very old female. Intermediate molar proportions. 

 Bridger C 5. 



126S3. Young adult male. Smallest molar proportions. 

 Bridger D. 



1511. Male. Small molar proportions. Bridger (?). 



12204. Very old female. Small molar proportions. Wa- 

 shakie D 2. 



2353. Female. Small molar proportions. Washakie A. 



The accompanymg table of measurements brings 

 out the following facts : 



1. In M. manteoceras there is a very considerable 

 range in size: Am. Mus. 1545 is larger in total skull 

 length than the type of M. wasliaMensis , but the first 

 and second molars are smaller. 



2. The molars in different specimens of M. manteo- 

 ceras are either microdont (Am. Mus. 12194, 12683, 

 1511, 12204, 2353) or macrodont (Am. Mus. 1545, 

 1570), but other measurements, especially the dimen- 

 sions of the premolars, do not confirm this division; 



1532. Male. Large molar proportions. Washakie A. 



1569. Type. Male. Large molar proportions. Washakie A. 



1570. Paratype. Large molar proportions. Washakie A. 

 1545. Old male. Largest molar proportions. Bridger 



D (?). 



13165. Female. Skull medium, cheek teeth large. Washa- 

 kie A, upper levels. 



2388. Type. Male. Skull and molars very large. Uinta 

 C, lower level. 



it does not seem to be due to sex, nor, so far as known, 

 to imply specific differences. 



3. M. wasliaMensis, from the upper levels of 

 Washakie A, is not much bigger in total skull length, 

 but it is more progressive in the relatively large size 

 of the molars. 



4. M. uintensis, from Uinta C, is far more advanced 

 than either M. manteoceras or M. washaJciensis in total 

 skull length (inferred), length of face, and all dimen- 

 sions of the dentition; but the molars are relatively 

 more advanced than the premolars. 



