OF THE WHITE EIVER BEDS OF MONTANA. 255 



M. 



Height of Pj , 012 



Length of M, 0095 



Length of M^ 0103 



Height of M f 010 



Length of M^ 017 



1 1 eight of skull above Mi about 062 



Hycenodon minutus, sp. nov. 

 Type No. 47. 



This consists of only a lower sectorial tooth, but it is so minute that it cannot be 

 confused with any known species, unless it be H. mustelinus, which is considerably 

 larger. It is the second molar of the right side. It shows considerable lateral wear on 

 the outside, showing that it was not a young animal. At the top of the cusp are two 

 beveled, worn surfaces, where the white dentine shows through the black enamel. The 

 dentine also is exposed on the anterior surface near the root. The tooth is thick in 

 proportion to its length. There are minute ridges on the anterior angles and a faint 

 median convexity. There is also a minute ridge in the posterior median surface. 

 Probably the most characteristic thing is the size. 



.Measurements. 



M. 



A 11 tero-postorior diameter 0075 



Transverse diameter 0040 



Prom Pipestone beds near Whitehall, Jefferson county, Montana, 



Colodon ri'tigulatus, sp. nov. 

 Type No. (52. 



Part of maxillary with PI, P 4 , Ml and base of P 2 . 



A prominent cingulum entirely surrounds the last two premolars. The internal 

 cusps — the deuterocone and tetartocone — are just beginning to divide, as indicated by a 

 shallow furrow on the inner side. The protostyle, protocone and tritocone are all con- 

 vex on the outside. The protocone and tritocone are nearly equal in size, but the pro- 

 tostyle is not so large or high. The metaloph is higher than the protoloph, the latter 

 nearly dying out before it reaches the protocone. in other words, it ascends steeply as it 

 passes outward toward the protocone. 



In M ' the paracone, parastyle, metacone and hypocone all appear as subcorneal cusps. 

 The parastyle is much smaller than the paracone, and is situated in front of it and does not 

 send backward a prominent cingulum on the outer face of the paracone as in G. procus- 



