350 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



cones; (5) the ectolophs are greatly elevated and con- 

 sist of the two well-defined subequal protocone and 

 tritocone convexities with a rudimentary external 

 cingulum and pronounced antero-external style; (6) in 

 p^ the progressive broadening tendency is illustrated 

 by the fact that the breadth (22 mm.) equals the length 

 on the ectoloph, a marlied advance upon what is 

 observed in either M. manteoceras or D. hyognathus — in 

 fact, this tooth now resembles p' in general pattern, 

 although retaining a more elongate contour; (7) in 

 p' the breadth considerably exceeds the length and 

 the crown is broadened internally by the expansion 

 of the deuterocone; (8) in p* we have a still more 

 quadrangular and molariform tooth, the length being 

 27 millimeters and the breadth 35, but in this tooth 

 the deuterocone is not quite so sharply defined. 



The superior premolars of the type (Am. Mus. 

 2060) are distinguished from the premolars of the 

 paratype (Am. Mus. 2004) by the following 

 characters: (1) The premolar series is somewhat 

 shorter (90 mm. as compared with 95 in Am. Mus. 

 2004); (2) p^ in the type is less advanced, in 

 that the deuterocone is smaller and placed 

 farther back and the tritocone is less subequal 

 with the protocone; (3) in p' also the deu- 



FiGURE 298. — Lower jaw of Telmatherium ulLimum 



One-fourth natural size. Am. Mus. 2060 (type). White River, Uinta Basin, Utah; base ot Uinta C, true 

 Uinta formation. 



terocone and tritocone are somewhat less progres- 

 sive and the tetartocone ridge is barely suggested; 

 the cingulum also is slightly less developed; (4) in p^ 

 the tetartocone is indicated by a low, obtuse swelling, 

 whereas in Am. Mus. 2004 it forms the distal spur of 

 a very prominent deuterocone ridge. These differ- 

 ences in the tetartocones can hardly be due entirely 

 to differences in degree of wear (the type being much 

 the older of the two), because in the paratype the ridges 

 in question are so strong that they would probably 

 show even in the worn stage. These differences seem 

 to indicate that the paratype is somewhat more ad- 

 vanced than the type in its premolar evolution. 



The inferior premolars, as observed in the lower jaw 

 of the type (Am. Mus. 2060), exhibit the following 

 characters: The postcanine diastema is about 20 milli- 

 meters in length; behind pi is a shorter diastema of 

 11 millimeters in length; pi and p2 are represented 

 only by the alveoli; pa is much damaged but was 

 incompletely molariform. 



P4 (ap. 27 mm., tr. 19) is submolariform, lacking 

 only the prominence of the postero-internal cusp, 

 which is analogous to the entoconid of the molars. 

 The trigonid is higher than the talonid, and its V less 

 sharply defined. A weak external cingulum appears 

 opposite the outer midvalley and festoons the external 

 slope of the hypoconid. 



Molars. — The superior molars are a powerful series 

 of teeth measuring 129 (type) to 137 (paratype) milli- 

 meters, with extremely elevated or subhypselodont 

 cusps, the ectoloph of the least worn m^ reaching a 

 height of 35 millimeters and the protocone of the same 

 tooth 24. The external cingulum is more pronounced, 

 especially in the type, Am. Mus. 2060, in which it 

 prominently guards the outer valleys and begins to 

 encircle the styles, reminding us of the cingulum 

 development in Menodus giganteus; the internal 

 cingulum is similarly prominent, embracing the entire 

 inner side of the crown in m^ of the 

 same specimen. A marked peculiarity 

 which is an advance on both M. 

 manteoceras and T. cultridens is the 

 prominence of the anterior cingulum in 

 m' to m', which swells into a large median 

 cingule, comparable to the protostyle of 

 most species of Menodus. The posterior 

 cingulum is less prominent except in m', 

 in which it is free and exceptionally high 

 (type); in the paratype it is connected 

 with an incipient hypocone swelling. 

 The elevated ectoloph is accented by the 

 sharp development of the parastyles, 

 mesostyles, and metastyles. The hypo- 

 cones of m^, m^ of both type and para- 

 type are very large and prominent, an 

 advance upon the conditions in T. 

 cultridens and T. validum. A fur. 

 ther peculiarity is that in the unworn paratype the 

 buccal surfaces of the internal cones (protocone and 

 hypocone) — that is, the surfaces facing the ectoloph — ■ 

 are somewhat flattened and vertically striate, instead 

 of rounded and smooth, as in M. manteoceras and D. 

 hyognathus, which is faintly prophesied in T. validum. 

 The only retrogressive elements are the conules, 

 which have disappeared. The conules are largest in 

 brachyodont titanotheres; with advancing hypso- 

 donty the base of the paracones and metacones ex- 

 tends linguad and either absorbs or crowds out the 

 conules. 



The inferior molar series represented in the jaw 

 associated with the type (Am. Mus. 2060) is of large 

 size (155 mm.). A smaller jaw (Am. Mus. 2033), 

 formerly referred to this species but now referred 

 provisionally to Manteoceras uintensis, is somewhat 

 shorter (147 mm.). Although this specimen probably 

 represents another genus and species, the molar 

 characters are somewhat similar to those of the type , 



