368 



TITANOTHERES OF ANCIENT WyOMING, DAKOTA, AND NEBRASKA 



but are of the mesaticephalic or subbrachycephalic 

 type. The dentition differs sharply from that of 

 Mesatirhinus and DoIicTiorMnus in the relatively short 

 diastema behind the inferior canines and the retarded 



Figure 307. — Skull of Manieoceras manieoceras 

 One-fourth natural size. Am. Mus. 1569 (type) and 1570. Washakie Basin, Wyo., level A 



Side view, 



view (reversed) of the tj^pe and paratype skulls 



development of the deuterocones and tritocones of 

 the premolars. 



Incisors. — The inferior incisors as seen in Am. Mus. 

 1566 approach the transverse or slightly arched posi- 

 tion observed in M. petersoni (Am. Mus. 1567) and 

 in DoIicTiorMnus. The perfectly preserved crown of 

 i2 indicates that this tooth is slightly larger than ii 

 and nearly if not quite as large as is; the posterior 

 face is smooth, with a faintly indicated basal cingulum. 



Canines. — The canines of the same jaw in the male 

 are estimated as 40 millimeters in height, 21 antero- 

 posterior, 21 transverse; they are implanted by 

 stout fangs which cause the outer face of the 

 ramus to bulge; faint anterior and posterior 

 ridges bound the convex inner face of the 

 canines; the diastema is much shorter than in 

 DoIicTiorMnus (17 mm. in No. 1566). The 

 superior incisors, partly preserved in Am. Mus. 

 1511, 1545, and fully preserved in Am. Mus. 

 12683, from Bridger D, are pointed, with a 

 posterior basal cingulum slightly more promi- 

 nent than in DolicTiorTiinus; in Am. Mus. 12683 

 they increase regularly in size from i' to i' and 

 at first sight resemble those of TelmatTierium 

 culfridens, but, as shown in Figure 309, they 

 are distinguished by their slightly smaller size, 

 weaker posterior cingulum, and less caniniformi^ 



The superior canines are robust, sublanceolate (that 

 is, with anterior and posterior ridges), tapering and 

 recurved; height 39 millimeters, transverse 26, antero- 

 posterior 24; they are provided with very stout fangs. 

 The postcanine diastema is very short, not exceeding 

 7 millimeters. 



Premolars. — The superior molar-premolar series, 

 although entirely broken away in the type specimen, 

 is superbly shown in five almost complete sets of 

 teeth. In general, as compared with the grinders of 



MesatirMnus and DoIicTiorMnus, we observe the 

 brachycephalic influence, indicated, first, in the rela- 

 tive shortness and breadth of each of the teeth, and 

 second, in the arching or posterior divergence of 

 the series, which is much 

 more marked than in Mesa- 

 tirMnus. The series meas- 

 ures from 176 millimeters in 

 Am. Mus. 12683 to 197 in 

 the old male No. 1545, as 

 compared with 160 in M. 

 megarMnus, and is about 20 

 millimeters greater than in 

 DolicJiorMnus. 



The chief distinctions of 

 the premolars from those of 

 MesatirMnus appear to be as 

 follows (Pis. LXVII, LXXII): 

 In M. manieoceras p^~* are relatively broader, the 

 deuterocones are not so wide anteroposteriorly and 

 lie farther backward, giving a more oblique contour 

 to the crown; the ectoloph is less hypsodont, its 

 anterior convexity is much broader, and its posterior 

 convexity is pronounced. The external cingulum, 

 while variable, is vestigial in Am. Mus. 1511, 2353, 

 and slightly indicated in Am. Mus. 1570, 1532. P' 

 is a simple, elongate tooth, bifanged; the tritocone 

 ectoloph is convex, and in certain specimens (Am. 

 Mus. 1511) the tritocone nearly equals the protocone 



Composite side 

 After Osborn, Am. Mus. Nat. Hist. Bull., vol.V, flg. 7, 1895. 



FiGUEE 308. — SkuU of Manieoceras manieoceras 



One-fourth natural size. Am. Mus. 12683, Sage Creek Spring, Bridger Basin, Wyo., level D. 

 Ai, Anterior half of skull; A2, cross section through malar and m^, showing flattened external 

 face of malar. 



in size; this tooth, nevertheless, still retains the 

 ancestral character of elongation and the marked 

 postero-internal position of the deuterocone. P^ is 

 slightly broader than long and exhibits various 

 degrees in the prominence and external convexity of 

 the tritocone; the external cingulum in the less worn 

 dentitions is well defined. No rudiment of the postero- 

 internal cusp can be discerned except in one very 

 large individual (Am. Mus. 1532), in which very faint 

 indications of this fourth cusp are seen in p^ and p*. 



