UPPER CRETACEOUS MARSUPIALIA 131 



more so than many early Tertiary species of Peratherium and not distinguished in any 

 important way from some certainly Tertiary didelphids of Patagonia itself. Its molars 

 do not show any of the remarkably various features which characterize the North 

 American upper Cretaceous fauna, but are of the one type which survived into the 

 Tertiary. Ameghino's figures do not compare at all closely with any Lance lower 

 molars, although it is possible that comparison of the original would reveal a greater 

 resemblance. In short, judged solely on its morphology, Proteodtdelfkys might well 

 be of Cretaceous age, but could equally well, or even better, be placed in the lower 

 Tertiary. 



There is much indirect evidence indicative of a faunal continuity between North 

 and South America in the upper Cretaceous. Until its age is exactly determined by 

 further field work and discoveries, Proteodtdelfkys is too doubtful to add anything 

 definite to this evidence and at the present time its importance, whether faunal or 

 morphological, is slight. It is not necessary to review the fantastic phylogenies of 

 Ameghino which make Proteodidel-phys ancestral to most later mammals. 



Proteodidel-phys praectirsor Ameghino 1 898 

 1898. P. fraecursor, Ameghino, Rev. Set. (4) X, 74. 



Xype. — Right lower jaw, with all teeth and complete save for upper part of coro- 

 noid. Fig'd, Ameghino 1900, figs. 2-5. 



Horizon and Locality. — PAreniscas abigarradas, Patagonia. (Exact locality 

 not published.) 



Diagnosis. — Sole species referred to the genus. 



Lance Lower Molars 

 Morphological variations in this group are great. Most of them may apparently 

 be broadly grouped under nine morphological types which are described below. 



Cimolestes Marsh 1889 (Type i) 

 1889. Cimolestes, Marsh, Amer. Jour. Set. (3) XXXVIII, 89. 



Definition.— Small Lance didelphid lower molars. Trigonid markedly higher 

 than talonid. Pr-* larger than me-^ and latter larger than pa-^. Pa-* strongly reduced. 



Type. — C. incisus Marsh. 



Distribution. — Lance, Wyoming. 



Cimolestes incisus Marsh 1889 

 1889. C. ineisus, Marsh, Amer. Jour. Set. (3) XXXVIII, 89. 



Type.— Y.P.M. No. 11775. Isolated lower molar. Fig'd, Marsh 1889A, PI. IV, 



figs. 12-15. 



Horizon and Locality.— Lance formation, Niobrara County, Wyoming. 

 Diagnosis. — Sole species now referred to the genus. 



