272 Annals of the Carnegie Museum. 



clays, and sandstones. Many bones of large dinosaurs have been 

 eroded from a stratum of clay in one locality north of Black Butte. 

 Above the clays containing the bones are series of clays and bedded 

 sandstones. The sandstones occasionally contain impressions of mol- 

 lusca, which are probably Jurassic. Above these shales and sandstones 

 on the west flank of the mountains in the Ruby Valley, are the lime- 

 stones which everywhere contain an abundance of gasteropods. 



At a considerable distance below the Dinosaur horizon are extensive 

 exposures of Carboniferous limestones. 



These observations will, perhaps, tend to show how indefinite are 

 the boundaries of different horizons of the Mesozoic of Montana. Not 

 only is this true, but no two sections from different regions appear to 

 be exactly alike. More careful study however may show that this is 

 partly due to conditions of exposure, disturbances of strata, etc. 



Lower and Middle Cretaceous. 



« 



The Fish- Creek Area. — Immediately overlying the quartzite on 

 the Joe Widdecombe ranch in the Fish-Creek section, are beds of red 

 and somber clays. As one stands on the top of the dome-shaped ex- 

 posure of quartzite, he sees on three sides of him bluffs of soft strata, 

 which have weathered into bad-land forms. The strike of the beds is 

 a circle or ellipse and the dip is in every direction outward from the 

 center of the hill. These beds, which are composed of sand and 

 sandy clay overlaid by thin-layered sandstones, contain bones of 

 large dinosaurs. Some beautifully preserved fresh-water mollusca were 

 found by Dr. M. S. Farr and Mr. A. C. Silberling. These constitute 

 a new faunule which was described by Professor Stanton, who says 

 concerning the age of the beds : "Although the evidence is not con- 

 vincing, the indications are that this fresh-water horizon near Harlow - 

 ton is not far from the horizon of the Bear River formation — possibly 

 contemporaneous with it — and that it is certainly not older than 

 Lower Cretaceous, and more probably should be assigned to about the 

 base of the LTpper Cretaceous. ® 



The following is the list given by Stanton : ^ 



Unio farri. 



Unio douglassi. 



^"A New Fresh -water MoUuscan Faunule from the Cretaceous of Montana," 

 Proc. Amer. Philos. Soc, Vol. XLII, No. 173, 1903, pp. 192 and 194. 

 ^/6i</., p. 193. 



