O. C. Marsh—New Orders of Jurassic Mammals. 237 
penultimate molar has four distinct cones instead of three. 
The canine was large, and directed well forward. The coronoid 
process is large, and inclined backward. The mylohyoid 
groove is nearly parallel with the lower margin of the jaw, and 
extends forward to the symphysis. The latter is large, an 
elongate. 
The main measurements of this specimen are as follows: 
Extent of lower molar series, ......-...--..--.. 14™™ 
Space occupied by premolars, ._--..--.---- his do Fa 
of jaw: below: cani@yces: asade- 3 - vs 3.0 
Depth of jaw below last premolar, .--.-.------- 3°5 
Depth of jaw below last molar, -.----.-..-.-.- 4°0 
Antero-posterior diameter of penultimate molar,. 3-0 
Heiphit of erewnpucs ois ieee adi. gi iz 2°5 
Triconodon bisulcus, sp. nov. 
Space occupied by three last molars,....-........ 8-0™™ 
Antero-posterior extent of last molar, .... ...._._- 2°0 
Depth of jaw below last molar, ................. 40 
Antero-posterior extent of penultimate molar,.._.. 2°5 
EADS 0 OW a ee 
Depth of jaw below last premolar, ..........._-- 30 
Dryolestes obtusus, sp. nov. 
Additional specimens of Dryolestes show that this genus 
possessed a peculiar dentition. There were no less than 
twelve teeth in the lower jaw behind the canine, and at least 
eleven in same series above. The upper molars had three 
external cones and one inner cusp, and this order was reversed 
in the lower molars. There was no cingulum above or below. 
The canines were small. 
The specimen on which the present species is based is a left 
upper Jaw, with the molar series nearly complete. The crowns 
