in the area, however, suggesting that this plant responds well to 

 fire. 



The lesser rushy milkvetch (A stragalu s convallarius ) is an 

 unusual prairie plant in this drainage, because this population is 

 more than 300 miles from the center of the species distribution in 

 the Great Basin area of southern Idaho and western Utah. This 

 species is found in scattered locations in the Helena Valley, 

 including residential areas and the Mount Helena City Park. The 

 Montana Rare Plants Project (MRPP) has recommended this plant be 

 listed as threatened. 



Another threatened plant found within this drainage is 

 trailing fleabane ( Erigeron f lagellaris ), commonly found in other 

 areas but known in Montana only from along the eastern front of 

 the Rocky Mountains. It grows in open meadows and prairies at 

 lower elevations including Falls Creek in Lewis and Clark County, 

 and the MRPP believes this population may be threatened by seismic 

 and other activities occurring at a nearby mining site. 



Geologic Features 



Seven percent of the Class I or II geologic feature sites 

 identified in the study, excluding type locations, were found in 

 the Missouri Basin from Three Forks to the mouth of the Smith 

 River. 



Along the Missouri River near Helena are several sapphire 

 mines where one can pay a fee and sort through gravel for 

 sapphires. Though not as brilliantly colored as the Yogo 

 sapphires found near Lewistown, they still are admirable gem 

 stones. Colors vary from pale blue to yellow and pink. These 

 sapphire mines receive considerable use during the summer months. 



Several of the small tributaries cut through deep limestone 

 canyons as they flow to the west out of the Belt Mountains toward 

 the Missouri River. Among these are Sixteen Mile Creek east of 

 Toston, Confederate Gulch on the east side of Canyon Ferry 

 Reservoir, and Beaver and Trout creeks between Holter and Hauser 

 reservoirs. A relatively undisturbed limestone canyon, 

 Refrigerator Canyon, which gets its name from the cool 

 temperatures within, can be reached with a short walk beginning at 

 the road up Beaver Creek. 



Near Hardy, the Missouri River flows through an area bounded 

 by reddish brown cliffs formed from volcanic conglomerate cut in 

 many places by igneous intrusions called dikes. The dikes extend 

 out into the plains west of Cascade and in several cases connect 

 the surrounding buttes, including Square Butte and Shaw Butte. 



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