28 DAVENPORT ACADEMY OF NATURAL SCIENCES. 



fossiliferous limestones. These are succeeded by shales and shaly 

 limestone which, through their whole thickness, are made "up of masses 

 of fossils, mainly of the Athyris vittata. These are again followed by 

 limestones resembling those in the upper portion, but more firm and 

 carrying some of the usual fossils. 



The contrast with the Spirifer Pennatus beds is very marked. There 

 are no alternations of light-colored limestones and shales, encrinal 

 limestones or coral reefs. These have disappeared. Another series 

 succeeds, in many respects widely different. The general construction 

 is heavy, massive. Thin layers of rock are not indulged in. The 

 shale is like no other shale. It is in full sympathy with the surround- 

 ings. There is nothing light or cheery about it. The mode of depo- 

 sition favors no such idea. And then comes in the color — drab, 

 uniform, persistent to the very last. 



There are no Corals, Crinoids, Gasteropods, Cephalopods, or Crus- 

 tacea. Brachiopods alone survive, their number greatly diminished. 

 Of these Prof. Calvin has furnished the following complete list: 



Spirifer parryanus Hall. 



Spirifer asper. Hall. 



Athyris vittata Hall. 



Cyrtina u?nbonata Hall. 



Atrypa reticularis Linnaeus. 



Terebratula Undescribed. 



Strophodonta Undescribed. 



To these none have been added since his publication. No exposure 

 of these beds occurs through the distance of seven or eight miles below 

 the city. They are then found in the First Ravine, over half a mile 

 north of the bluff. A small hillock stands in the very midst of the 

 stream, m,ade up of the buff limestones and accompanying shales, the 

 latter filled with the usual smaller fossils. Within a short distance two 

 or three other patches appear. Another equally limited exposure is 

 seen in the Second Ravine, and about the same distance from the 

 bluff. Fossils had been found in the bed of the stream from time to 

 time, but no trace of their origin, until very lately. A little rivulet 

 had found its way down from the top of the hill, hewing into the shales 

 and limestones of the Spirifer Pennatus beds until a succession of steps 

 of unequal thickness was formed extending down to the main stream. 

 On mounting these, at the very summit appeared for the first time the 



