268 THE WASATCH AND BRIDGER FAUN^. 



ICTOPS DIDELPHOIDES Cope. 



Bulletin U. S. Gcol. Snrv. Terrs., vi.p. I9i, Febniary 26, 1881. 

 Plate XXV a, fig. 9. 



Established on a left niaiKlihular raniu.s, which supjjorts the last three 

 inolar.s. This demonstrates the t'oi-mer existence of a species of larger size 

 than any of the LeptktidcE hitherto known. The general form of the infe- 

 rior true molars is a good deal like that of Stypolophus, but they may be 

 distinguished by three characters in whic h they at the same time agree with 

 the htops biatspis: First, the elevated border of the heel, with a strong 

 external cusp and weaker posterior and internal elevations ; second, the 

 small development of the anterior cusp ; third, the posterior production of 

 the heel of the third true molar, giving an indication of the fifth lobe. The 

 external anterior cusp of tlie third molar is elevated ; on the first molar it is 

 less so, and the anterior cusp is small. The enamel is smooth, and there 

 are no internal nor external cingula. The mandibular ramus is compressed 

 and deep. 



ileasuremerits. 



M. 



liength of bases of three true molars 01C5 



anteroposterior 0055 



0038 



Diameters of first tTue molar/ . , , ■ V 



( transverse belinul 



anteroposterior 0060 



transverse 0050 



Depth of ramus at anterior root of last true molar 0095 



T^- .^ ^. . 1 , ( anter 



Diameters ol last tnio molar? , 



( transverse 0050 



The jaw fragment described indicates a skull about the size of that of 

 the common opossum. 



PERATII KlilUiM Aymard. 



Berpctotherium Copt, Paleontological Bulletin No. 16, ji. 1, August, 1873. Annual Report U. 8. Geol- 

 Surv. Terrs., F. V. Hayden, 1873 (1874), p. 465. 



9 1 '-i 1 



Dental formula: I. - ; C. ; Pm. ^ ; M. . Fourth su])cri(tr iPiviiiolar 



like the true molars, with two external cusjjs and an internal one; third pre- 

 molar compressed, with one lobe. Inferior molars with heel supporting 

 cusps at the angles, and the three cusps anteriorh-, of which the e.xterior is 

 most elevated and the two inferior subcqual. fourth premolar with the 

 anterior internal cusp WL'll developed; the other inferior premolars simple. 



