SMITHSONIAN EXPLORATIONS, I929 27 



was made to find Cambrian sections not previously noted. Here giant 

 pines and tamaracks break the monotony of the typical Rocky Moun- 

 tain forest. Leaving this region we visited various ranges in south- 

 western Montana, all of which are composed of the same extensive 

 series of pre-Cambrian sediments but lack younger beds. It is only in 

 the ranges that the rocks are free from drift cover, which explains the 

 method pursued, namely, crossing as many ranges and divides as pos- 

 sible. In some cases we used roads that are seldom traveled, least of 

 all by automobile, but as a reward we usually found the streams full 

 of trout. After going as far southwest as Salmon, Idaho, we turned 

 eastward, crossing several ranges that still contained only the pre- 

 Cambrian strata, finally reaching a Cambrian section on Camp Creek 

 near Melrose, Montana. Since the rivers have rather easy grades for 

 the most part and since snow l)anks at some of the higher levels per- 

 sist until August, the mosquitoes hold on here almost all summer. We 

 attempted to camp one evening at the end of July near Wisdom, but 

 as soon as the car stopped we were at once enveloped in a cloud of 

 mosquitoes, consequently we drove on up to Big Hole Pass, camping 

 within sound of running water, although it was too dark to see the 

 stream. This proved to be a fortunate location as eight trout were 

 secured for breakfast within 15 minutes next morning while the 

 fishing line froze stifi^. Sul)sequently other sections in the Jefiferson 

 Range were studied and some of them measured. 



We then turned to Logan and again met Dr. Moraes. Accompanied 

 by him we made a loop to the northward, visiting ])articularly the Belt 

 Mountains where Dr. C. D. W'alcott had obtained interesting algal 

 forms more than 15 years ago. Geologists have at times questioned 

 the organic origin of these structures, and Dr. Moraes. who is attempt- 

 ing to solve certain ])roblems in Brazil, wished to see these deposits 

 in the field and thereby learn the criteria which led those of us who had 

 previously studied them to believe in their organic origin. 



Along the south end of the Belts in the canyon of Dee]> Creek cer- 

 tain shale beds of the Belt series have yielded fragmentary organic 

 remains that have been inter]>reted as animal. These outcrops were 

 located and some specimens secured. If these f(^ssils could be proven 

 to be animal remains they would constitute the oldest such examples 

 known. But our studies have thrown much doubt on the animal 

 nature of the fossils, indicating rather that they were algae akin in ap- 

 pearance at least to the flat sea-weeds of today. This inteqn-etation is 

 still further strengthened by the discovery of quite similar forms in 

 the overlying Cambrian beds concerning whose algal nature there can 

 be no doubt. 



