VI. ON THE CRANIAL ELEMENTS AND THE DECIDU- 

 OUS AND PERMANENT DENTITIONS OF 

 TITANOTHERIUM. 



By J. B. Hatcher. 



Among other material collected by the Carnegie Museum Paleonto- 

 logical Expedition of 1900 there is a skull and considerable portions 

 of the skeleton (No. 116) of a young Titanothere. This was found 

 near the base of the Titanotherium beds about three miles north of the 

 Brewster and Emmons ranch on Warbonnet Creek, in Sioux Co., Ne- 

 braska. The skull and lower jaw are of especial interest, since, owing 

 to the immature age of the individual, most of the cranial sutures are 

 still open, making it possible to determine the character of the differ- 

 ent bones. Moreover the milk dentition is still preserved, so that it 

 is possible to determine its nature, while the permanent dentition is 

 sufficiently advanced to indicate definitely the method and, order of 

 replacement of the deciduous by the permanent teeth. 



The Skull. 



When viewed from above the frontals are much the more conspic- 

 uous elements. They are bluntly rounded posteriorly and are projected 

 far backward beneath and between the lateral anterior projections of 

 the parietals. Anteriorly the frontals are continued into two long 

 lateral projections which extend beyond the orbits, overlie the ]:)0ste- 

 rior and lateral margins of the nasals and give rise to the pair of horn 

 cores that form such characteristic features in the Titanotherids. The 

 nasals are arched superiorly, concave inferiorly, with rather long pos- 

 terior extensions interposed between the frontal horns. In the present 

 specimen the nasals are very thin along their inner margins but much 

 thickened externally and posteriorly, where they give the chief sup- 

 port to the horns. They are slightly shorter than the premaxillaries 

 and somewhat emarginate anteriorly. 



The parietals are not so broad as the frontals. ' They are deeply 

 emarginate anteriorly and posteriorly, where they are separated by the 

 interparietal portion of the supraoccipital much as in Equus. From the 



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