124 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 52 



geologist, and never fails to fill his basket with fine shells, beautiful 

 corals, and sometimes, but not very often, with rare crinoids." 



These little descriptions sometimes contain matter of a more scien- 

 tific nature than the one just quoted, in witness of which is the 

 following {Spirifer gregaria, page 120) : 



"This species is found abundantly in the Corniferous limestone at 

 and around the Falls of the Ohio, in Kentucky and Indiana. It 

 appears here silicified, in well-preserved specimens of the whole 

 shell, as well as of the separatee! single valves. Specimens still in- 

 closed in the limestone are of the same material. From observa- 

 tions made by me at the Falls of the Ohio, and which, undoubtedly, 

 were also made by other geologists, who visited and examined that 

 world-renowned storehouse of Devonian fossils, but of which I 

 never found any notice in print, I am forced to the conclusion that 

 the silicification of the shells and corals is produced by their expo- 

 sure to water and weather, and that this process requires only a 

 comparatively short time. Whenever, at low stages of the water, 

 the bed of the Falls becomes dry, we find it entirely covered by fossil 

 shells and corals, partly exposed above the solid rock and partly in- 

 closed in the same. All the exposed fossils which have been acted 

 upon by water and weather for some length of time are silicified, as 

 far as they are above the matrix, while the inclosed parts are still 

 limestone, or, if a change in their material has already commenced, 

 the silicification has not sufficiently advanced to resist the dissolving 

 power of muriatic acid, which has not the least influence upon the 

 exposed parts. In the same condition are the fossils found in the 

 fields near the Falls in Kentucky and Indiana. Those which are 

 entirely weathered out, and the parts of others freed from the 

 matrix, are silicious, while the inclosed parts have retained their 

 original material." 



This explanation of the silicification of fossils has been held by 

 few geologists, but in the opinion of the present writer Mr. Nettel- 

 roth's general idea is correct and can be verified from many other 

 observations. 



The most valuable part of the Nettelroth collection was derived 

 from the Silurian, Devonian, and Lower Carboniferous strata out- 

 cropping in the vicinity of Louisville. The quarries and other ex- 

 posures along Bear Grass Creek have long been known to paleon- 

 tologists for the many fine Silurian and Devonian fossils yielded by 

 them, while the outcrops at the Falls of the Ohio are recognized the 

 world over as a storehouse of Devonian fossils. The accompanying 

 photographs are of some of the best-known fossil localities in the 

 vicinity of Louisville. Of most interest, probably, is the celebrated 

 Falls locality shown in figure i, plate x. Here, at times of low 

 water, great stretches of Devonian limestone are exposed with a 

 new lot of fossils showing every year. The choicest specimens on 



