136 AMERICAN MESOZOIC MAMMALIA 



As intimated above (lower molars, type 8) it is very probable that the lower 

 molars of this sort are deciduous teeth of one of the more usual didelphids. The upper 

 molar syntype has been mislaid or lost, an ordinary small Pediomys upper molar now 

 being preserved under this number. Search of the extensive Yale, American Museum, 

 and National Museum collections failed to reveal another like it except one which is 

 broken, — a first upper molar or deciduous upper molar of Pediomys, sens, lat., with the 

 cingulum broken off. Such imperfections are very difficult to observe, especially with- 

 out the aid of a binocular, and in the absence of the original some suspicion must 

 remain that this was the character of the upper tooth figured by Osborn. I f this is not 

 the case and Osborn's view is confirmed by further discoveries, Synconodon is entirely 

 unlike anything else known and is a very novel element of uncertain affinities in the 

 Lance fauna. 



Archaeoplus Amt^hino 1898 

 1898. Archaeo-plus, Ameghino, Sin. Geol. Pal., Seg. Cen. Nac, I, 174. 



Species. — A. incifiens, Ameghino 1898, loc. cit., genotype. Type: a supposed 

 incisor. 



This form, of wholly doubtful age and affinities, has already been discussed in 

 dealing with Proteodidelfhys above. 



"Telacodon^' praesfans Marsh 1892 

 1892. T. fraestans. Marsh, Amer. Jour. Set. (3) XLIII, 258. 



Type. — U.S.N. M. No. 2133. Fragment of lower jaw with two molars. Fig'd, 

 Marsh 1892A, PI. IX, fig. 4. 



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



There is no positive basis for referring this species to Telacodon, as the type is not 

 directly comparable with the genoholotype. Such reference is not impossible, but the 

 morphology of the teeth suggests that they are rather the lower molars of a didelphid 

 and the species is of very doubtful status. 



Order INSECTIVORA Gray 1827 



Under this heading three Lance genera are to be discussed, Gypsonicto-ps, Tela- 

 codon, and Batodon. None of these is well known, Gypsonictops resting on isolated 

 upper teeth, P* to M*, and the other two each on the anterior part of a lower jaw. Gyp- 

 sonictops is of considerable importance as it seems to prove that there is a minor 

 placental element in the dominantly multituberculate-marsupial Lance fauna. The 

 other two are also probably placental, but the evidence is less clear. Their reference to 

 the Insectivora does not rest on any tangible ordinal characters subject to definition, 

 but on resemblances to later mammals, difficult of formal recognition but sufficiently 

 definite to justify this allocation even aside from theoretical considerations. Gypsonic- 



