2^2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



Obscure fragments of gastropods and brachiopods occur 162 

 feet up and again at 350 feet up in a thin layer of light-gray, fine 

 arenaceous limestone and a dark layer above 575 feet. 



Noted: Stromatopora, Strcptclasma, Heliolitcs. 



Sections of brachiopods and a gastropod. 



lb. Light-gray, arenaceous limestone that forms a strongly 

 marked, even-topped, low cliff, towards the summit. Strike north 

 60° west (magnetic). Dip 23° southwest 180 feet. 



Numerous small, cherty nodules occur in association with bits 

 of silicified Stromatopora, with thinner layers near the top. 



This limestone is succeeded liy limestones referred to the 

 Carboniferous. 

 Carboniferous 



la. Bluish-gray, thin-bedded limestones with cherty nodules 

 and layers of chert in some of the layers. (Layers 1-6 in., 12 in., 

 24 in., thick.) 



This band begins at a saddle west of the slope on the top of ic, 

 and is a marked feature on the north side of Beaver Creek beneath 

 the massive, gray, conglomerate limestone cliffs. Total of ia..78o feet. 



At 375-400 feet noted fossils, and at 740 feet from the base a 

 fauna, in which the following species have been identified by Dr. 

 George H. Girty of the United States Geological Survey : ^ 

 Chonetes loganensis 

 Productus ovatus 

 Productus semireticidatns 

 Productus gallatinensis 

 Piistula scabricula 

 Camarotoechia metallica 

 Spirifer centronatus 

 Bcllcrophon sp. 



lb. Light-gray arenaceous to almost pure granular limestone in 

 massive beds. In places carries cherty nodules. Weathers rough, 

 forming jagged cliffs. 



At 1,225 feet from the base of ib corals occur and at 1,850- 

 i,goo feet up the corals are in great abundance. 



Masses of Diphophyllum 2 to 3 feet in diameter. 

 Syringopora, etc., etc. 



Total of lb 2.075 feet. 



ir. Shaly sands with interbedded bands of gray limestone and 

 sandstone. 



At about 600 feet up remains of Bryozoa are abundant. The 

 section is here broken by the canyon of the Missouri River. On 

 the west side of the river high cliffs of sandstone, etc., rise fully 

 1,000 feet back from and above the river. 



^ " I would unhesitatingly call this fauna Carboniferous and also unhesitat- 

 ingly call it Mississippian. It appears to represent the horizon of the Madison 

 lirhestone. It is not, however, the most typical phase of the Madison fauna, 

 which is of early Mississippian age, and I would not state positively at this 

 time that it might not belong in the middle Mississippian. Even so, it would 

 be within the limits of the Madison limestone as they are at present recog- 

 nized." (Information in letter from Dr. Girty, of April 5, 1916.) 



