538 E. RUSSELL LLOYD AND C. J. HARES 



formation and the Lance of other areas. The fossil seaweed, Halymenites 

 major, which is common in the Fox Hills and other sandy formations of the 

 marine Cretaceous, is also associated with the above listed fauna. 



FORT UNION FORMATION 



West of Missouri River Fort Union formation overlies the 

 Cannonball member of the Lance and on Little Missouri it overlies 

 the Ludlow lignitic member of the Lance. In this part of the 

 Dakotas a large part of the formation has been removed by 

 erosion, but in Billings County, North Dakota, one of the writers 

 (Hares) has found a thickness of 1,025 feet. The formation consists 

 of calcareous sandstone and shale of continental origin, contain- 

 ing numerous thick persistent beds of lignite and an abundant 

 flora and fresh -water invertebrate fauna. Some of the thick 

 lignite beds have burned extensively, and great numbers of red 

 hills composed of fused and baked rock are characteristic features 

 of the formation. The lower 100 feet of the formation is made up 

 almost wholly of partially consolidated yellow and gray fine- 

 grained sandstone which is in some localities indistinguishable from 

 the sandstone at the top of the Cannonball member. At numerous 

 other exposures, however, where the upper bed of the Cannonball 

 member is a sandy shale, the contact is easily followed. At one 

 locality on the north bank of Heart River in Tp. 136 N., R. 88 W., 

 there is an erosion channel from 30 to 50 feet deep in the Cannon- 

 ball member filled with the channel deposits of a Fort Union stream. 

 Similar channel sandstones at the base of the Fort Union were 

 seen along Little Missouri, near Yule, and at the mouth of Deep 

 Creek, and also on Sand Creek, in Billings County, North Dakota. 

 These strata show evidence of a rapid change in the character of 

 the sedimentation. They consist predominantly of coarse sand- 

 stone containing lenses or pockets of conglomerate and of soft 

 clay shale. The conglomerate consists of pebbles derived from 

 the strata of the surrounding region and contain numerous water- 

 worn bones, teeth, fish scales, fragments of silicified wood, and 

 lignite in the form of tree trunks. Among the vertebrate remains 

 are two mammalian teeth which have been identified by Dr. J. W. 

 Gidley of the U.S. National Museum as Euprotogonia sp., second 

 lower molar of left jaw, and Pantolamda cavirictus, upper premolar. 

 Both of these species are found in the Fort Union beds of Sweetgrass 



