Cope.] "10 [Dec. 7, 



and a part of a mandibular bone with the last two molars in place, all be- 

 longing to different individuals. The inferior sectorial tooth is much like 

 that of the D. leptomylus, but the tubercular is only two-thirds as long, and 

 is not only absolutely, but relatively narrower posteriorly. It has the 

 usual three cusps in a reduced condition. In the first superior true molar 

 the external cusps are conical, and there is a small cusp between the ante-, 

 rior one and the produced anterior angle of the crown. There is an ante- 

 rior intermediate tubercle, but no posterior one. The cingulum does not 

 extend all round the inferior base of the crown, as it does in D. protenus. 

 The sectorial has a distinct anterior basal conic lobe. The internal lobe is 

 in transverse line with the last named, and is conical and not large. 



Measurements. M. 



Diameter inferior sectorial { anteroposterior 0138 



t transverse 0055 



Diameterinferior tubercular { anteroposterior 0050 



I transverse 0033 



Depth of ramus at M. i 0098 



Diameter superior sectorial (No. ^(anteroposterior. . . .0110 



t transverse 0060 



Diameters superior sectorial (No. 2) { anteroposterior . 0050 



t- transverse 0090 



The fourth specimen is especially important as presenting almost the 

 entire dentition including canines and incisors, and the anterior part of the 

 skull from the line of the coronoid process of the mandible. The specimen 

 shows that the species differs from the species of the "Wasatch period with 

 oval inferior tubercular, in the absence of the posterior cutting lobe of the 

 third, and probably fourth inferior premolar. The corresponding superior 

 premolars are also simple. The first premolars in both jaws are one- 

 rooted. The canines are long and acute, and are directed vertically. Both 

 have flat facets on their external (the only visible) faces : on the superior 

 canine I count four lateral, and one nearly anterior. On the inferior I see 

 three lateral and one nearly anterior. There are three small superior in- 

 cisors, of which the first is the largest, and has a subcorneal crown. The 

 infraorbital foramen is large, and is above the anterior border of the supe- 

 rior sectorial. 



Measurements. M. 



Length of superior dental series to front of canine 041 



" " crown of superior canine 011 



" " superior true molars 0105 



Depth of ramus at inferior sectorial 0090 



In its simple premolars this species agrees with the D. haydenianus, and 

 is more primitive than the Wasatch species. 



Tktisodon rustictj.8, sp. nov. 



Founded on a portion of the mandible which supports the first two true 

 molars and part of the last premolar. The species is of the type of T. 



