NO. 6 PALEOCENE FAUNAS OF BISON BASIN — GAZIN 37 



P. acolytus and P. Icmuroides. Presumably P. acolytus (Cope), the 

 first of the two listed by Trouessart, is to be regarded as the genotype. 



MEASUREMENTS IN MILLIMETERS OF TEETH IN SPECIMENS OP 



Promioclaenus pipiringosi 



U.S.N.M. 



No. 2 1 02 I 



P2, anteroposterior diameter : greatest transverse diameter 2.7 : 1.6 



Ps, anteroposterior diameter : greatest transverse diameter 3.3 : 2.1 



P4, anteroposterior diameter : greatest transverse diameter 3.8 : 2.8 



U.S.N.M. 



No. 20571 



(type) 



Ml, anteroposterior diameter : greatest transverse diameter 4.1 : 3.4 



M:, anteroposterior diameter : greatest transverse diameter 4.4 : 37 



PROMIOCLAENUS? sp. 



A very large species of Promioclaenus may be represented by a 

 fragmentary right mandibular ramus (U.S.N.M. No. 21020), having 

 preserved only the posterior portion of M2 and part of the trigonid as 

 well as the roots of M3. The form is close in size to Litaletes disjunc- 

 tiis Simpson of the Montana Fort Union. M3 would appear to be 

 fully as large as in L. disjunctus, a relative size quite unlike typical 

 Ellipsodon. There is a distinct possibility that this is Litaletes rather 

 than Promioclaenus ; however, the cusps included in the preserved 

 portion of M2, though somewhat worn, suggest a lower crowned tooth 

 as in Promioclaenus, distinctly less inflated than in Mioclaemis. 



LITOMYLUS SCAPHICUS,!^ new species 

 Plate 8, figures 2, 4 



Type. — Right ramus of mandible with M2 and M3, U.S.N.M. 

 No. 21014. 



Horizon and locality. — Bison basin Tiflfanian, saddle locality at 

 south rim of Bison basin, sec. 28, T. 27 N., R. 95 W., Fremont 

 County, Wyo. 



Specific characters. — Lower molars larger and relatively wider than 

 in Litomylus dissentaneus. Cusps relatively lower and more inflated, 

 with paraconid more reduced. 



Discussion. — There would seem no doubt but that the genus Litomy- 

 lus, originally described by Simpson on the basis of the species L. dis- 

 sentaneus in the Torrejonian of the Montana Fort Union, is repre- 

 sented by two distinct species in the Bison basin Tiffanian. Litomylus 



^^ Skaphikos, from Greek j/;o/>/joj = anything hollowed out as a basin, in allu- 

 sion to the Bison basin. 



