642 LAND MAMMALS IN THE WESTERN HEMISPHERE 



have very similar trenchant and fluted teeth, but in that 

 family the lower one of the pair is the last premolar, not the 

 first molar. Marsupials of this type have not been foimd in 

 formations older than the Deseado. 



The relationship of these South American genera to the 

 Australian phalangers is a very interesting question from the 

 standpoint of mammalian distribution, but is not likely to 

 receive a positive answer until something is learned regarding 

 the history of the Australian family. 



Suborder fALLOTHERiA 



This extinct suborder is still very imperfectly understood, 

 for it is known almost exclusively from jaws and teeth ; so far, 



the skull of one genus and 

 most of that of another have 

 been obtained, but hardly any- 

 thing of the skeleton. The 

 fAllotheria were small or mi- 

 nute marsupials, herbivorous 



Fig. SOS.-SkJuTof Paleocene fallothere OT OmuivOrOUS, wMch had lost 

 {^Ptilodus gracilis), enlarged, Fort Union all trace of the CaniueS and 

 stage. (After Gidley.) .... 



had one pair of incisors above 

 and below, which grew from persistent pulps and had a scal- 

 priform, rodent-like character. The molars were composed 

 of numerous tubercles (whence the name " fMultituber- 

 culata," often applied to the group) arranged in two or three 

 longitudinal rows, and the premolars were either like the 

 molars, but of simpler pattern, or compressed, sharp-edged and 

 trenchant. The t-'^Uotheria were among the most ancient 

 of mammals and have been found in the Triassic of Europe, the 

 Jurassic of Europe and South Africa, the Jurassic and Cre- 

 taceous of North America and the Paleocene of both northern 

 continents, while the South American Eocene (Casa Mayor) 

 had certain problematical genera (fPolydolopidse), which may 

 be referable to the fAllotheria or to the Ccenolestes series. 



