EUCROTAPHUS OF NEBRASKA. 



563 



The crown of the penultimate premolar is a transversely compressed cone, having 

 developed at its base antero-internally, and in a less degree postero-internally, a 

 basal ridge. 



The upper temporary true molar is quadrilateral, with the inner three sides com- 

 bined into one convexity, and is longer than it is broad. It is constructed after the 

 type of the permanent true molars, but the anterior basal ridge and the inner 

 mammillary eminences are relatively not so well developed. 



The penultimate premolar presents the characteristic elongated form of the tem- 

 porary tooth of the series in most Ungulata. It looks as if formed by a prolongation 

 of the anterior lobes of a tooth like the last temporary molar, and the association 

 of its anterior mammillary eminences into a single one. The inferior permanent 

 true molars present a striking resemblance of form to those of the Peccary, with 

 which Archceotherium is a near relative. They present in outline the figure-of-8 

 form, and all present two transverse pairs of mammillary eminences, with a feebly 

 developed basal ridge anteriorly, and a thicker and tuberculated ridge posteriorly. 

 The latter of the last molar is not better developed than in those in advance. A 

 peculiarity of these teeth of Archseotherium is the division at summit of the 

 antero-internal lobe into two. The fragment of the last inferior temporary molar 

 preserved in the specimen, is constructed on the same pattern as those just 

 described, and, as in most Ungulates, had six lobes to the crown arranged in three 

 transverse rows. 



The last permanent premolar, which had not yet protruded, and is partially 

 exposed only in the specimen, appears to have the same form as the penultimate 

 premolar above. 



From none of the permanent molars being worn to any extent in the specimen, 

 the enamel presents a remarkably wrinkled appearance, particularly upon the sides 

 of the eminences of the true molars. 



ADMEASUREMENTS. 



Estimated length from the summit of the inion to the commencement of 



the nasal bones, ....... 



Length from occipital condyle to the lachrymal process, 

 Breadth of skull at zygomge, ...... 



" " cranium at middle of temporal surface, .... 



" at suture crossing the post-orbital arch, .... 



" of face at the anterior true molar alveoli, .... 



EUCROTAPHUS. Leidy. 

 EUCROTAPHUS AURITUS. Leidy. 



(Tab. xv., figs. 1, 2.) 



The genus Eucrotaphus was proposed in the Proceedings of the Academy, vol. v., 

 page 92, upon a posterior portion of a cranium, remarkable for the large relative 



Inches. 



( i 



7 



8 



O J 



