CREODONTA. 281 



molar. The last true molar is cut off obliquely on the external side and 

 posteriorly, so that the posterior external cusp stands on the posterior ex-' 

 ternal angle of the ci'own. The posterior cingulum is strong on all the 

 true molars, and extends i-ound the inner base of the ci'own. It is strongest 

 on the first and second, but does not rise into a cusp on either, as it does in 

 Pelycodus and other forms. 



The probable inferior canine has a characteristic form. The crown is 

 not elongate, and the section of its base is a half circle. Above the base 

 the inner face becomes concave, a broad median ridge dividing the con- 

 cavity into two grooves, which are less marked near the apex. There is a 

 shallow groove external to the posterior edge, which is thus acute; apex, 

 obtuse. The inferior molars, except the first and last true molars, have been 

 described above The first true molar does not differ from the second. 

 The anterior part of the third is just like that of the second, but the heel 

 is much longer. I cannot give the details of its form, as the surface is in- 

 jured. 



Measurements, 



M. 



Length of superior dental series from canine 043 



Length of diastema 005 



Length of premolar series 017 



Diameters of canine^ ^°*«'°I'°**«"°'^ ^°^ 



< transverse OOG 



Length of precauine diastema 007 



T^- . Ti • Mransverse 008 



Diameters, Pm. iv< . „„. 



c anteroposterior 00/ 



Diameters, M. ii5 tr^^isverse 009 



c anterposterior 008 



TV- i ,r ... 5 transverse at middle 009 



Diameters, M. iii< 



< anterposterior 006 



Length from incisive border to jiostorbital angle 056 



Width between superciliary edges 030 



Length of true inferior molars 033 



Length of last inferior molar 0098 



Depth of ramus at M. ii 0155 



This species was a half larger than the common opossum, and was 

 much more robust. The typical specimen was found by Mr. D. Baldwin at 

 the mouth of Canyon Largo, on the San Juan River, Northwestern New 

 Mexico, in the Lower Eocene formation. Mr. Baldwin informs me that it 

 came from below all the Wasatch Sandstones, which would place its horizon 

 in the Puerco formation. The other specimens came from about the same 

 position. 



