MORRISON MAMMALS: PANTOTHERIA 



79 



enamel is entirely gone and the crowns are reduced to mere shapeless stumps. It has no 

 morphological interest so far as the teeth are concerned, but it does reveal a little of the 

 palate. The choanae were narrow and the posterior end of the palate cuts straight 

 across to them from behind M^. 



Euthlastus Simpson 1927 

 1927. Euthlaslus, Simpson, Amer. Jour. Sci. (5) XIII, 414. 



Definition. — Pantothere upper jaws, molars more than four and probably seven. 

 Crowns cordiform, with hook-like anteroexternal cusps. Outer border of two rounded 

 lobes separated by median notch, an outer marginal cusp on the anterior lobe, but none 

 on the posterior lobe. Two posterior marginal cusps. Crowns essentially broad basins 

 with raised rims and elevated internal apex. Last three molars broader than long. 



Type. — Euthlastus cordiformis Simpson. 



Distribution. — Morrison formation, Wyoming. 



Euthlastus cordiformis Simpson 1927 

 1927. E. cordiformis, Simpson, Amer. Jour. Sci. (5) XIII, 414. 



Type. — Y.P.M. No. 13755. Right maxilla with last four molars, all somewhat 

 broken. 



Horizon and Locality. — Morrison formation, Quarry 9, Como Bluff, Wyoming. 



Diagnosis. — Sole species of the genus. Total length of last three molars about 

 2.2 mm. 



Dentition 



The first tooth preserved is too broken to be of much value. It is farther out of the 

 alveoli than the others, no doubt from fost mortem causes. The last three teeth are alike 

 in essentials. They are cordiform in contour, as the specific name indicates, save for an 

 irregularity due to the projection of the 

 anteroexternal cusp. The point of the he- 

 raldic heart outline is internal and is pro- 

 duced into a high, slender, piercing cusp. 

 Its concave external face passes downward 

 into a broad shallow featureless basin 

 which constitutes the whole effective grind- 

 ing area of the crown. The edge of this 

 basin is sharp and slightly elevated all 

 around it. The outer edge of the external 

 anterior lobe is occupied by a marginal 

 cusp, the internal face of which (toward 



the basin) is concave. Posterior to this is a ^ .lj . jt • a i,ct *«.„ ^„»,* 



' Fig. 32. Euthlastus cordtformts. A, last four ngnt 



marginal notch which separates the outer ^pp^^ molars, crown view, type. B, restoration of 

 lobes. The external margin of the posterior crown view of upper molar. 25 times natural size. 



"YPMUFSS 



