NIAGARA FALLS AND VICINITY I07 



bedding lines may be observed occasionally, indicating that the 

 fragments were subject to wave action. The stratum varies in 

 thickness from 5 to 6 feet, and is occasionally divided by horizontal 

 sutures which show a marked stylolitic structure similar to that 

 found in the crystalline upper Clinton limestone. The contact be- 

 tween this and the underlying stratum is wavy. This rock has been 

 quarried at Lockport under the name of Lockport marble. 



Geodiferous limestones. The crinoidal limestone is succeeded by 

 strata all of which are more or less geodiferous, though varying con- 

 siderably in composition and structure. 



4) The rock immediately following on the crinoidal bed 

 is a 4 foot stratum of compact, gray fossiliferous limestone, 

 the fossils being of a fragmentary character. Stratification struc- 

 ture is well marked on the weathered surfaces, specially in 

 some of the lower beds of the stratum. Sometimes there is 

 only one thick bed, at others the stratum consists of a number of 

 thin beds with a heavy one near the center. The thin beds show 

 the stratification structure best, having at the same time a strongly 

 granular character. As the fossils are fragmentary, and only ac- 

 cessible on the weathered surfaces, little is known of the organisms 

 that constitute it. Crinoid joints occur, but they are less character- 

 istic of this than of the lower stratum. Geodes however are not 

 uncommon, the cavities being lined with crystals of pearl spar (dolo- 

 mite) or filled with masses of snowy gypsum. 



5) The fifth stratum of limestone in this series is a finely crystal- 

 line magnesian rock, like the others destitute of fossils except in 

 so far as these are represented by geodes. The latter are common 

 and filled with alabaster, or sometimes with massive or crystallized 

 anhydrite. The latter is distinguished from the crystallized gypsum 

 or selenite, which it closely resembles, and which occasionally occurs 

 in the same beds, by the cleavage, which is rectangular and nearly 

 equally perfect in three directions in anhydrite, while it is perfect 

 in one direction only in the selenite. 



6) A finely crystalline, somewhat concretionary dolomitic lime- 

 stone, 3 feet thick, next succeeds, the weathered sectional surfaces of 

 which, buff in color, show the fine stratification structure, which 



