UPPER CRETACEOUS MARSUPIALIA 133 



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

 Diagnosis. — Sole recognized species of the genus. 



Didelf/iodon ferox was based on a badly worn and broken lower molar (Y.P.M. 

 No. 1 1828) which appears to be conspecific with the type of D. curtus. Didelfhodon 

 ferox was published a page previous to Cimolestes curtus, but the latter name is re- 

 tained as the former was based on an inadequate type. 



Delphodon Simpson 1927 (Type 3) 

 1927. Delfhodon, Simpson, Amer. Jour. Set. (5) XIV, 127. 



Definition. — Trigonid little higher than talonid. Pa-^ and me'' nearly equal, pr"* 

 equal or slightly higher. Talonid large and basined, with three well defined cusps. HP 

 and en'' approximated. Anterior cingulum not prominent, not basined. 



Type. — D. comftus (Marsh). 



Distribution. — Lance, Wyoming. 



A great many teeth, with considerable range 

 in size and some variation in proportions, fall un- 

 der this genus, taken broadly. It certainly includes 

 several species of lower molars and possibly more 

 than one natural genus. Its relative abundance, 

 variation, and generalized character suggest that 



this genus includes the lower teeth originally asso- 



.^j.,, ,, r J4.DJ- Fig. 51. Lance pediomyine. Fragment 



ciated with the uppers referred to Pediomys,sensu ^^ ^^^^ ^^^^^ ^^^ ^^^ ^^ ^^,^^^ 



lato. At the same time, this association is not y.p.m. No. 10685. 

 proven and the tj^e species is certainly not con- 

 generic with Didelfhodon ferox Marsh and can hardly have belonged with Didelfho- 

 don vorax, the genotype. To avoid incorrect association, it has therefore been necessary 

 to erect a new genus for Marsh's species, and it is also convenient to have a name which 

 may properly designate these most common of Lance lower molars. Since this memoir 

 was completed, Russell (1928) has given the name ">. Delfhodon fra^nuntius to one 

 sort of teeth of this group. The holotype is 4.6 mm. in length and has the pa'' and me'' 

 close together. Many such names could be proposed for the varied teeth of this type. 



Type 4 



Trigonid little higher than talonid. Vr^ and me'' nearly equal, pa'' higher. Three 

 talonid cusps, but hi'' and en'' imperfectly separated. Large. 



This is close to Diafhorodon and may represent a different part of the dentition of 

 that genus. The chief difference is in the markedly lower protoconid. 



Type 5 

 Trigonid higher than talonid. Pr'' much the highest cusp. Pa'' and me'' subequal. 

 Talonid strongly marked off from trigonid. Very small. 



