2 



Measurements. M. 



Diameter of base antero-posteriorly 1060 



" ' ' transversely 0800 



" of summit 0650 



Projection of nasal cornice beyond apex 0630 



Length posterior molar, crown 0450 



Width " " " 0550 



This species is equal in size to the largest known from the Bridger 

 formation. It differs from Eobasileus (Loxolophodon) comutus in the 

 angulate base of the posterior horn-cores, the acute supra-temporal 

 ridge, the stoutness of the median cores, and extent of their inner face, 

 covered by the nasal bones, and the relatively greater width of the 

 second true molar. It much more nearly resembles the Eobasileus pres- 

 sicomis, Cope, and may possibly prove to represent an old male of that 

 animal. There is, however, a considerable disparity in their sizes ; the 

 horns differ in the greater stoutness, having twice the diameter, with 

 little greater height. They differ also in form and in the abrupt con- 

 traction just below the apex. The cornice-like cores of the nasal bones 

 represent the tubercles of the E. pressicomis. The posterior horns 

 differ in many ways from those of the E. furcatus, and are alone suffi- 

 cient to indicate a different species. 



From the bad lands of South Bitter Creek. 



Archaenodon insolens. Gen. et sp. nov. 



Char. Gen. Dentition of mandible. In. 3 ; C. 1 ; P. m. 3 (? 4) M. 3 ; 

 forming an uninterrupted series throughout. Molars consisting of two 

 pairs of obtuse tubercles, those of each pair fused transversely by a lower 

 yoke. Last molar with a large posterior fifth tubercle. Last premolar 

 enlarged, and with a posterior heel ; penultimate with a simple conic 

 crown and two roots. It is uncertain whether one or two teeth intervene 

 between this one and the canine. The alveoli are round, and look as 

 though designed for two single-rooted premolars. 



This genus presents many points of resemblance to Eloth&rium, but 

 the continuous dental series is characteristic of many genera of the 

 Eocene. In the only known species there are no osseous tuberosities on 

 the rami. The symphyseal suture is persistent. 



Char, specific. Last premolar with longer basis than first molar ; its 

 posterior heel tubercularly plicate. The crown of the penultimate pre- 

 molar is a slightly compressed cone with elongate base, but little shorter 

 than that of the first molar. Molars with smooth enamel ; an anterior 

 cingulum on the second and third. A small posterior median tubercle 

 on the second molar, and a short cingulum from the base of the posterior 

 cone forwards, on the third. Canines very large, sub-erect, enamel 

 smooth. Ramus of mandible very stout. 



