MORRISON MAMMALS: PANTOTHERIA 



83 



with raised margins bearing, aside from the hook-like anteroexternal heel which is 

 excluded from the basin, a marginal, ridge-like anteroexternal cusp and one median 

 cusp on the posterior margin. Posteroexternal angle raised slightly but not truly cusp- 

 like. 



Type. — Pelicopsis dubius Simpson. 



Distribution. — Morrison formation, Wyoming. 



Pelicopsis dubius Simpson 1927 

 1927. P. dubius, Simpson, Amer. Jour. Set. (5) XIII, 414. 



Type. — Y.P.M. No. 13754. Right maxilla with last three molars. 



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



Diagnosis. — Sole species of the genus. Lengths of last three molars 1.3, 1.3, and 

 0.8 mm. respectively. 



Dentition 



From the proportions of the teeth preserved, it seems probable that this genus had 

 less than seven molars, possibly only four or five. From this fact and from the shape of 

 the interdental embrasures it is unlikely that it is a dryolestid and it is not improbable 

 that it is a paurodontid. 



The antepenultimate molar is a 

 stout tooth, its crown slightly longer 

 than broad. The internal cusp is 

 broken, but it was by far the largest 

 and highest cusp of the tooth. The top 

 of the crown is a broad shallow basin 

 with the rim raised all around it. The 

 anterior rim is a crest running straight 

 externally from the anterior limb of 

 the subcrescentic internal cusp. Near 

 the external border it rises to form a 



YPH ;o?~s'^ 



Fig. 35. Pelicopsis dubius. Last three right upper mo- 

 lars, crown view, type. 25 times natural size. 



ridge-like cusp, presumably the homologue of the centroexternal cusp in Herfetairus 

 and Melanodon but much less pronounced than in those genera, and it then curves pos- 

 teriorly and is continued in the external rim of the basin. The posteroexternal angle is 

 slightly raised, but there is no true cusp here. On the posterior border, however, about 

 halfway to the internal cusp, is a cusp-like rising of the elevated rim. The anteroexter- 

 nal cusp is excluded from the basin and has the usual rather heel-like form, but it is 

 not so hooked as in Euthlastus, for example, or as in the more posterior molars of this 



same specimen. 



The penultimate molar differs only slightly from the foregoing. It is broader, but 

 of about the same length. The anteroexternal cusp of the elevated rim is less prominent. 

 There is a faint trace of a median ridge in the basin at the base of the internal cusp. 

 The outer surface of the anteroexternal heel is more hemispherical and its apex is 

 pushed slightly inward and is more hook-like. 



