FAUNA OF THE MEXDOTA LIMESTONE. 175 



is hard and of a buff color. The lowest bed seen is a s(^ft dolomite in 

 sight for about 4 feet. ]McGee sa3's : 



" The limestones are ma^iiesian, always more or less sandy, and generally heavy 

 bedded or massive ; the shales are imperfectly lissile, commonly calcareous and 

 sometimes richly fossiliferous, as at Lansing, where they are charged with fine 

 specimens of Dlcellocephalns minnesoteiisis and other characteristic Upper Cambrian 

 forms." * 



The vSaint Lawrence is essentially a dolomite, yet at the top it shows 

 an interlamination of di)lomite and sandstone, which appears to be the 

 transition from this formation to the overlying Jordan sandstone. 



FA UXA L CIIA RA CTERS. 



The faunal characters of the formation are not marked. It may be 

 said, however, that fossils have been found in nearly every exposure 

 examined in the three states under consideration. The representative 

 species are : 



Dikellocephahis minnesotensis, Owen. 



Lingula aurora, Hall. 



Lingula mosia, Hall. 



Orthfs j)epina, Hall. 



Raphistioma minnesotensts, Owen. 

 For collecting the most productive places are perhaps Osceola, Hudson, 

 Trempealeau and Lone Rock, Wisconsin; Marine Mills, Redwing, llokah, 

 Minnesota, and Lansing, Iowa. 



The Jordan Sandstone. 

 localities. 



In Minnesota, Jordan, Ottawa, Mankato, Minneopa falls, Rapidan, 

 section 12 Judson, Stillwater, Hastings and the whole length of the 

 Mississipi>i river in the state, Bear creek, above Stockton on the Winona 

 and Saint Peter railway, and RoUingstone. 



In Iowa, Lansing and McGregor. 



In Wisconsin, Lone Rock, lake Mendota and Madison, Osceola, and 

 Hudson. 



SPECIAL FEATURES. 



At Jordan, Minnesota, this sandstone has its t3'pical outcrop. It 

 occurs on Sand creek, about half a mile above tlie village. In the bed 

 of the creek it seems somewhat calcareous. The color is reddish at tlie 



• Eleventh Annual Report U. S. GeologicHi Survey, 1889-'90, p. ?:.V.',. It is to bo noted that Mr McGoo 

 includes these beds in the Potodam. 



XXV-Bui.i.. Oeol. Hoc. Am., Vol. fi. 1H94. 



