16 Annals of the Carnegie Museum. 



exposure of the very fissile green shale member. The green shale is 

 from sixty to seventy feet thick and contains numerous bands of 

 greenish and grayish limestone concretions, which are usually very 

 fossiliferous. From many horizons in the lower forty feet of the green 

 shale, pyritized fossils, chiefly cephalopods, often beautifully preserved, 

 weather out on the surface and furnish excellent collecting. Above 

 the green shale at this locality is about ten feet of very fossiliferous 

 gray limestone which weathers reddish on the surface. Overlying this 

 limestone are thirty or forty feet of yellowish shales, grading upward 

 into calcareous sandstones. Above the yellow sandstones is the gray 

 Madison limestone with fossils of Mississippian age. This section 

 northeast of Crane was not measured carefully with a tape, because 

 many of the contacts were obscured by talus or vegetation. However, 

 enough of the section was exposed to show that it closely resembles 

 the sections to the south at Rekap and Logan. 



Section B. — The section next south of Lombard is near Rekap Station 

 on the Northern Pacific Railway. The strata here strike N. 30°-35° E. 

 and dip 30° W. The section was measured from the base of the 

 gray Madison to the top of the brown Jeft'erson limestone and includes 

 the following seven members: 



I and 2. Yellow sandy limestone and shale 74 feet. 



3. Black coaly shale 6 " 



4. Nodular gray limestone 7 " 



5. Fissile green shale ~1 



and Y 120 " 



6. Gray and orange limestone. J 



7. Pebbly yellow and reddish limestones and shales 80 " 



Total 287 feet. 



The Three Forks formation was measured at two localities near 

 Logan, Montana. One section was near the Gallatin River and the 

 other was about two miles inland. The strata here strike about N. 

 50° E. and dip 40°-50° W. 



Section C, measured near the Gallatin River, is as follows: 



Base of gray Madison limestone. 



1. Yellow arenaceous limestone 30 feet. 



2. Pale yellow arenaceous shale 30 



3. Purple fissile shale .5 



4. Bluish gray nodular limestone 9.5 



5. Fissile green shale 47 



6. Yellow crystalline limestone with calcite veins 15 " 



Massive grayish brown limestone 12 



7. Yellow and orange blocky shales 78 



Total 222 feet. 



