B. S. Lull — Mammals and Horned Dinosaurs. 325 



Of these Brown says the multituberculates and trituber- 

 culates " are unmistakably those of the Lance, but the placental 

 mammals have not been found in the Lance and appear to 

 belong to the Palseocene groups of mammals, although they do 

 not compare closely with Puerco or Torrejon genera. This 

 layer was located in the bluff at a point 150 feet above the 

 river. Apparently it was a local deposit, an old river channel 

 of the Paskapoo period which crossed the present river at 

 right angles. Twenty-five feet above the mammal stratum 

 there is a bed of shells 8 inches thick, from which Doctor T. 

 W. Stanton has identified JJnio sp., Sphcerium sp., Goniobasis 

 tenuicarinata, Planorbis sp., Viviparus sp., Campeloma sp., 

 which he says are suggestive of Fort Union rather than earlier 

 forms." 



Matthew (1914, p. 388) has checked up Brown's identifica- 

 tion of the mammals and agrees with his findings and conclu- 

 sions. He says in addition, in speaking of the apparently 

 Palseocene element in the fauna: 



" I suspect that it will be found to compare more nearly with 

 the Fort Union fauna. It is evident at all events that there was 

 a considerable element of placental mammals in the fauna. But 

 the Multituberculates are those of the Lance and some of the 

 Trituberculates appear to be identical. There is no indication of 

 the presence of any of the Eocene orders of placentals." 



Comparison with the Fort Union fauna. — A comparison of 

 the Lance with the Fort Union brings to light a number of 

 similarities and still more marked discrepancies. The Fort 

 Union mammals are known from several localities, all of which, 

 with one exception, are in the neighborhood of Fish Creek in 

 Sweet Grass County, south central Montana, a region the 

 importance of which was enhanced by Douglass' discovery of 

 these interesting types. 



Silberling (Stanton 1909, p. 261) separated the Fort Union 

 into three members, of which number 1, the lowermost, and 

 number 2, the intermediate, together constitute the softer, 

 darker-colored shales and sandstones with a combined thickness 

 of about 1300 feet, while the upper member, or number 3, con- 

 sists of massive sandstones interbedded with shales, and is more 

 than 4000 feet thick. The last member is identical with the 

 whole of the Fort Union of Stone and Weed. 



The middle member, Fort Union number 2, is the one 

 wherein the most important mammal collections were made, 

 and from a quarry 65 feet below the top of the formation on 

 the east side of Bear Butte, Mr. Gidley has recognized the fol- 

 lowing (classification after Matthew) : 



