A Geological Reconnoissance. 185 



The shaly layers last described, some barren and some con- 

 taining beautifully preserved remains belonging to a great 

 number of organic species, make up the Yellozv shales beds. 

 No. 7, of the section published in the Geologist, September, 

 1 891. A mile or more above Littleton the yellow shales with 

 their characteristic fauna are exposed in the bank of the west 

 branch of the Wapsipinicon. The exposure is at the foot of 

 a bluff sixty or seventy feet in height, and outcroppings at 

 different elevations in the bluff show that the beds up to the 

 summit are yellow calcareous shales, hard enough with the 

 exception of a few layers near the level of the water, to resist 

 the action of the weather. No orgranic remains were observed 

 in the bluff except in the few feet of soft shales near the base. 

 All the strata of the bluff belong properly to the Yellow shales 

 beds, and when added to what is exposed below the mill at 

 Littleton, they give to this member of our Devonian section a 

 great predominance, so far as thickness is concerned, over all 

 the others thus far noted in this paper. West of Jesup, in the 

 edge of Blackhawk count}-, the Acervularia beds are seen in 

 place. At Waterloo the same beds are exposed. At Ra}-- 

 mond, between Jesup and Waterloo, quarries are worked in a 

 hard yellowish calcareous shale which I take to be the equiv- 

 alent of that part of the Yellow shales beds exposed above the 

 base of the bluff near Littleton. 



Between Littleton and Fairbank no rocks were seen in 

 place. A quarry on the west side of the stream at Fairbank, 

 contains thick bedded strata the exact relations of which were 

 not ascertained. The rock is an impure limestone with a con- 

 siderable admixture of clay. The fauna is scanty, consisting 

 chiefly of a Cystifhyllmn of unknown species and one or two 

 species of ?ie-ujherria. Specimens of Acervularia weathered 

 from higher beds were found on the surface but no diagnostic 

 species were seen in place. Neither the Cystiphyllum nor 

 the Newberrias could be said to be absolutel}' identical with 

 any known species. A mile or two up the stream, at a place 

 called Cedar Bluffs, rocks are exposed, but they reveal 



