FORT UNIOISr OF CRAZY MOUNTAIN FIELD, MONT. 



235 



the tip. There is a distinct parastyle and small vague metastyle. 

 The entire crown is circled by a cingulum which bears a cusp, topo- 

 graphically a metaconule, near the middle of the posterior border. 



Figure 62.- 



-Ellipsodon aquUonius Simpson, U.S.N.M. no. 9280, right lower jaw: a, Crown view; 6, in- 

 ternal view. Two and one-half times natural size. 



Figure 63.— Ellipsodon aquUonius Simpson, U.S.N.M. no. 9567, with parts in outline supplied from 

 U.S.N.M. nos. 9571 and 9576; left upper jaw: a, External view; b, crown view. Four times natural size. 



M^ and M^ have the same structure but differ in size and proportions. 

 Although distinct, the paracone and metacone are crested and the 

 crests tend to form a simple ectoloph. The protocone is crescentic 

 and its wings bear definite protoconules and metaconules, just internal 

 to paracone and metacone. There is a sharp, continuous external 

 cingulum, small definite parastyle, very vague metastyle, and no 

 mesostyle. The pronounced anterior cingulum stops short at the 

 anterointernal corner without rising or rounding the long mternal 

 slope of the protocone. The otherwise similar posterior cingulum 



