16 THE NAUTILUS. 



of Devonian, and capped by Upper Burlington limestone. The 

 Chouteau fossils, especially the crinoids, are interesting, and the 

 type specimen of one species came from Mt. Vernon, while Provi- 

 dence has given the types of many fossils. 



The most of the shells found at both places are now found living 

 in the neighborhood, while others have not been found in any nearby 

 county. The following species have been collected : 



Polygyra profunda Say. The largest of the Providence shells 

 are of 31 mm. diameter, but the Lupus shells up to 34 mm. averag- 

 ing smaller size, but more plentiful and some preserving the color 

 band. So far this has not been found living in the state except at 

 Courtney, in Jackson County, near Kansas City. 



Polygyra albolabris alleni Weth. At both places fine shells from 

 26 to 32^ mm. diameter are common, and more plentiful at Lupus. 

 The living shells have been found in the neighborhood to about the 

 same size, but from a rock pile in an open field near Columbia they 

 were only 23 to 25 mm. and very similar to the still smaller ones 

 found in a cemetery at Kansas City. 



Polygyra thyroides Say. Of fifty shells picked up at Providence 

 thirty-six were thyroides edentata, and of thirty-seven at Lupus 

 twenty-five were the same. 



Polygyra elevata Say. Not much variation in size, somewhat 

 smaller at Lupus, and all similar to the living ones found on both 

 sides of the river. Some that seemed to have been entirely mature 

 were edentate. 



Polygyra clausa Say. Scarce at both places. 



Polygyra pennsylvanica Green. This is rather uncommon at both 

 places. A walk of three miles along the railroad, during which 

 many thousand shells were picked up or seen, gave but a single one 

 of this species. It is not now found living in this part of the State. 



Polygyra appressa Say. These are of the three-tooth variety 

 found rather plentifully in many places in Missouri. On both sides 

 of the river the shells vary much in size, many being larger than 

 those now living in the neighborhood. It is the most plentiful shell at 

 Providence, but scarce at Lupus. The shells variedjn size from 15 to 

 22 mm., and many of the smaller ones have only a trace of lip teeth. 



Polygyra inflecta Say. Sparingly found at both places, but some- 

 times uncertain as to whether fossil, or simply dead shells that had 

 dropped from higher parts of the bluff. 



