196 BULLETIN UNITED STATES GEOLOGICAL SUEVEY. [Yol.Yl. 



The appearance of the ridges of the anterior part of the jaw of the 

 Bathyopsis Jissidens, together with the remarkably large dental canal 

 and mental foramen, strongly suggest that the animal possessed a large 

 and perhaps prehensile lower lip. 



PEEISSODACTYLA. 



34. Pal^osyops borealis Cope. 



American Naturalist, 1880, p. 746. 



Founded on a portion of the right maxillary bone, which supports 

 the three true molars and one premolar. Size of Limnohyus fontinaUs, 

 or much smaller than P. Icevidens. Anterior median tubercle well de- 

 veloped ; anterior and posterior cingula strong, not rising to inner cones. 

 A low ridge extending outwards and forwards from posterior cone. En- 

 amel smooth. Differs from P. junior Leidy in the presence of the inter- 

 mediate tubercle and crest, and in the weak external cingulum. Length 

 of true molar series, .063 ; diameters of first true molar, anteroposterior, 

 .019; transverse, .020. 



Portions of several individuals were obtained by Mr. Wortman. 



35. Lajmbdotherium POPOAGICUM Cope. 



American Naturalist, 1880, p. 748. 



Char. gen. — Dentition much as in Limnohyus, excepting that there is 

 a diastema in front of the second inferior premolar. Presence of first 

 inferior premolar not ascertained. Fourth inferior premolar without pos- 

 terior cusps. Superior molars with an angular ridge extending inwards 

 from each inner cusp. Last inferior molar with heel. This genus 

 differs from Oligotomm in the simplicity of the fourth premolar, which 

 has in the latter two posterior cusps. The Y-shaped crests of the in- 

 ferior molars separate it from Hyracotherium. 



Char, specif. — The heels of the second and third premolars have a 

 median keel ; the third only has an anterior tubercle. The crest of the 

 heel of the fourth forms an imperfect Y. Heel of the last true 

 molar small. No cingula ; enamel smooth. Length of molar series, .080 ; 

 of true molars, .044 ; of last molar, .019 ; depth of ramus at first premolar, 

 .021 ; at last molar, .031. Second specimen : Diameters of crown of last 

 superior molar, anteroposterior, .014 ; transverse, .016. About the size 

 of the Hyrachyus agrestis. 



This species was probably the most abundant perissodactyle of the 

 epoch of deposit of the Wind Eiver beds. 



36. LAirBDOTHERIUM BEOWNIANUM Sp. nOV. 



Considerably larger than the L. popoagicum, and about equal to the 

 Tapirus terrestris. The greater part of a lower jaw represents the 

 species, and on this unfortunately only one of the premolar teeth 

 remains. The three premolars are all two-rooted, and the posterior lobe 

 of the last true molar is well developed. The inferior part of the exter- 



