1898.] Osborn, Evolution of the Amblypoda. Parti. 171 



This compression is an essential character of the Periptychidae. 

 The upper and lower molars of Protolambda, HI., A and Al, on 

 the other hand, resemble those of the Pantolambdidse. 



rr' .hr" 



A — 



Fig. I, Lara'he Trituberculates. 



C. Synconodon sexiatspis. Upper and lower molar types. Nos. 2218, 2220. Am. Mus. Coll. 

 F. Ectoconodon petersoni. Upper molar types. Nos. 2224, 2223. Am. Mus. Coll. 

 A. Protolanibda hatcheri. Upper molar types. Nos. 2201-3. ^'^^- Mus. Coll. 



I^ower molars Hl^ yJ/ (possibly correlated), Nos. 2241, 2230, 2231. Am. Mus. Coll. 



These types may now be defined as follows : 



Synconodon, gen. nov. 



73;/^t'.— Isolated upper and lower molars. Am. Mus. Coll., Nos. 2218, 

 2220. 



Definition. — Molars long and narrow. Trigons laterally compressed, 

 primary cones approximated. Talonid well developed. 



S. sexicuspis, sp nov. 



Definition. — Talonid of lower molars with three cusps, hypoconid, hypo- 

 conulid, entoconid. Type as above. F'ig. i, C. 



Ectoconodon, gen. nov. 



Type. — Isolated superior molars Loc, Laramie. Am. Mus. Coll., Nos. 

 2223, 2224. 



Definition. — Superior molars very broad. Trigon laterally compressed. 

 Two external prominent cones (parastyle and metastyle), reinforcing the outer 

 wall of the crown. 



E. petersoni, sp. nov. 



Superior molars with conules and a rudimentary mesostyle. Type as 

 above. Fig. i, F. 



