239 



inches. The first lobe is nearly obliterated, and its back plate conjoins the 

 contiguous one of the second lobe. 



Another specimen consists of the back part of a molar with six lobes, 

 occupying a space of nearly 4^- inches. The lobes exhibit the same narrow, 

 elongated, pal mated form, with curved digitate extremities, as in the molar 

 fragment from New Mexico. The first of the six lobes is worn off at. the 

 summits of the digitate ends. The others are unworn, and the second plate 

 is 3§ inches wide near its middle. 



MEGACEROPS. 



Megacerops coloradensis. 



An imperfectly known extinct animal, which was supposed to be related 

 with the great ruminant, the Sivatherium of the Tertiary formation of the 

 Sewalik Hills of India, is indicated by a singular looking fossil discovered in 

 Colorado. The specimen belonged to Dr. Gehrung, of Colorado City, by 

 whom it was presented to Professor Hay den. It is represented one-half the 

 natural size in Figs. 2, 3, Plate I, and Fig. 2, Plate II, and was originally 

 described in the Proceedings of the Academy of Natural Sciences of Phila- 

 delphia for January, 1870, under the name heading this article. 



The fossil is singularly puzzling in its character, and possesses so little in 

 common with the homologous portion in ordinary animals that its relation- 

 ship would have remained unknown, or entirely conjectural, had we not bejen 

 previously acquainted with the Sivatherium. The specimen appears to cor- 

 respond with that portion of the face of the latter which comprises the upper 

 part of the nose, together with the forehead and the anterior horn-cores. As 

 is described to be the condition in the corresponding portion of the skull of 

 Sivatherium, all the bones entering into the constitution of the fossil are 

 completely co-ossified, so as to leave no traces of the original course of the 

 sutures. The nasal and contiguous bones are of great thickness, and as solid 

 as those generally in the living Sirenians. 



The horn-cores of the Colorado fossil resemble the anterior ones of Siva- 

 therium both in form and relative position. Thej^ are large, dense, conical 

 knobs, somewhat trilateral, and with a rounded, dome-like summit, which is 

 more porous on the surface than any other part of the fossil. They are 

 nearly straight, and divergent from each other, and their summits project 

 more over their base externally than in Sivatherium. 



