RemarJcs on the Geology of Western JYew York. 245 



has been considered peculiarly characteristic of transition rocks, also 

 occurs in the superincumbent shale. It has been found at the mouth 

 of Eighteen Mile Creek, on the shore of Lake Erie. Specimens 

 may also be seen at Mr. Barnett's museum at the Falls, found in that 

 vicinity. In speaking of the trilobite family, Dr. Thompson, in his 

 recent work on Mineralogy and Geology, says that " no traces of 

 them have been discovered in the lias, nor new red sandstone, nor 

 even in the coal beds." 



With the cornitiferous strata above described, terminates what I 

 believe to be the upper transition limestone. The superincumbent 

 strata present a mixed character. The fossils are mostly the same 

 as those already mentioned ; showing that the same animals contin- 

 ued to inhabit the same seas ; while on the other hand, the thin 

 beds, or rather insulated patches of bituminous coal, mostly, I should 

 think, the product of single plants, begin to make their appearance ; 

 showing likewise, that some portion of the earth's surface near by, 

 had emerged from the waters, and was in a fit condition to support 

 the growth of vegetables. I have not even here met with the im- 

 pression of leaves, he. but farther research may yet bring them to 

 light. 



The lower portion of these strata, where seems to commence the 

 change from the transition to the coal formation, are mostly com- 

 posed of soft shale or slate, sometimes bituminous, and containing 

 large quantities of iron pyrites. This shale alternates with strata of 

 impure limestone from one inch to one foot in thickness, which also 

 contain iron pyrites disseminated and forming a thick coating on their 

 under surface. The lower portion of this shale contains more or 

 less carbonate of lime, varying from the least perceptible quantity 

 to one half or more of its weight ; constituting a marl of great value 

 fqr agricultural purposes. It is principally in this marly state that 

 the fossil shells occur. Many of the bivalves are exceedingly per- 

 fect, retaining all the delicate markings on their exterior surface ; 

 while others are twisted and contorted in a singular manner. Oth- 

 ers again are in a collapsed state, one valve having been crushed 

 in, as if done by great pressure. Beds of this marl have been 

 opened in Geneseo and South Avon, where it was mistaken for gyp- 

 sum, and used as such in the vicinity ; and it would seem, from the 

 results, with equal advantage to the agriculturalist. One specimen 

 from South Avon yielded thirty six, and another sixty per cent, of 

 carbonate of lime. In neither could I detect any sulphate. 



