0, C Marsh — Notice of New Tertiary Mammals. 525 



The two forms may readily be distinguished by the last 

 apper molar, which, in the latter species, lias the middle 



anterior cusp situated almost directly between the outer and 

 the inner cones. In the present specimen, this cusp is placed 

 in front of the other two, the posterior margin of its base 

 reaching only to the middle of the main cones. 



The postorbital processes are long, and more nearly close the 

 orbit behind, than in the other known species of this genus. 



The space occupied by the last six teeth of the upper 

 premolar and molar series is four and three-fourth inches, 

 and by the corresponding low^er series, five inches. The 

 distance from the last upper molar to the back of the occipital 

 condyles is four and one-half inches. 



Limnohyops laticeps, gen. nov. 



In 1872, the writer described a large mammal from the 

 Eocene of Wyoming under the name Palceosyops laticeps* 

 A- the name Palceosyops has since been restricted, this species 

 must be regarded as representing a distinct genus, which may 

 be called Limnohyops. In this form, the last upper molar has 

 two inner cones, and in Palceosyops, as now defined, there is 

 only one. 



New Haven, Conn., May 21, 1890. 



*This Journal, vol. iv, p. 122, August, 1872. 



