656 THE WASATCH AND BEIDGER FAUN^. 



rior border. The third premolar is injured. The fourth has a complete 

 anterior transverse crest with a slightly concave edge. There is a strong 

 anterior basal cingulum. The heel is wide and supports two cusps, a larger 

 external one and a smaller internal one. The former is trihedral in section 

 and is wrinkled on the inner face. In the other inferior molars the trans- 

 verse crests have entire edges, and there is a narrow anterior basal cingu- 

 lum, rather elevated in position. There is also a rudimental posterior one, 

 but none on either internal or external side. Length of molar series, .064; 

 of true molars, .040; of last true molar, .016; depth of ramus at second 

 premolar, .020; at third true molar, .030. 



In a third specimen of lower jaw, both of the last molars are preserved. 

 Their cross-crests are entire and with slightly concave edges. The heel 

 is- well developed. The only cingulum is a weak one in front. Each 

 extremity of the second cross-crest sends an angular ridge downwards and 

 forwards. Length of last inferior molar, .0155; length of heel, .0040; 

 width at anterior cross-crest, .0087. 



Heptodon calciculus Cope. 



Lophiodon calciculus Cope, Americam Naturalist, 18S0, p. T47. Pachynolophus calciculus Cope, Bulletin 

 U. S. Geol. Snrv. Terrs., VI, 197, Feb. 26, 1881. 



Plate X:XIXo; fig. 6. 



The mandibular rami of two individuals of this species are in my col- 

 lection. One of these contains all the molars except the first (second), with 

 most of the diastema. As the maxillary teeth are unknown, it is not yet 

 certain whether this species belongs to the genus to which I have referred 

 it, or to Lophiodon. In one of the lower jaw^s there is a single-rooted first 

 premolar on the side of the crest of the diastema. It is wanting in another, 

 and is probably an inconstant character. 



This speciee differs from the P. ventorum in the possession of a single 

 external posterior crest on the fourth premolar instead of two posterior 

 tubercles. It is also considerably smaller, and the heel of the last inferior 

 molar is smaller. The lateral ridges which descend anteriorly from each 

 transverse crest are very little marked on the true molars, and there are no 

 oblique ridges. There is a rudimental anterior basal cingulum, which is 



