I02 DAV1 NPORT ACADEMY OF NATURAL S< [EN( I . 



and arc less argillaceous than those portions of the beds which are ex- 

 posed at Rockford and Hackberry. The fossils in this region are very 

 abundant and finely preserved. The species Naticopsis qigantea 

 attains a somewhat larger size and is more abundant than in some 

 other portions of these beds. 



On a small creek, at Owen's Grove, in Cerro Gordo County, the 

 annexed section was taken : 



i. Drift and detritus (sloping surface, probably concealing 



several feet of shaly limestone), by estimate 17 feet. 



2. Soft, dark buff, somewhat argillaceous shaly limestone . 7 



3. Blue shaly limestone, containing concretions 2% " 



Total 2(,'j feet. 



About one-eighth of a mile south-west from this locality, on the same 

 creek, is another limited exposure of the shales, which differ in some 

 particulars from those exposed at any other locality, in that they 

 weather to a rather sofr, yellowish-while clay, and contain numerous 

 Lamellibra'ichiata and Gasteropoda not known to occur in other por- 

 tions of the beds. 



Six miles east of Clear Lake, the shales are seen to outcrop on Wil- 

 low Creek. They are here somewhat thicker bedded than usual, and 

 vary from a dark buff to a dark brown color; they vary, also, from 

 their equivalents previously described, at other localities, in being 

 slightly sandy. The fossils are not numerous, and nearly all occur in 

 the form of casts. 



Two miles east of Clear Lake, the shales are observed as an outlier 

 in a gently undulating prairie region, and present the same paleontolog- 

 ical and lithological character (except that they are somewhat more 

 friable) as at the exposure on Willow Creek. 



Three miles west of Mason City, in the west bank of Willow Creek, 

 the shales are again finely exposed, and at this locality the following 

 measurements, by estimate, were taken : 



1. Drift i foot. 



2. Thin bedded, shaly, argillaceous limestone, containing 



some sand and casts of fossils, decomposing readily on 

 exposure 20 feet. 



3. Hard, stiff blue clay, containing numerous concretions of 



harder material 12 " 



Total 2>2> f eet - 



The fossils contained in the shales at this place are comparatively 

 rare, and occur only in the form of poorly preserved casts. 



