BUFFALO SOCIETY OF NATURAL SCIENCES 117 



Naples quadrangle, Ontario County, the Bertie is a hard, dark, im- 

 pure, hydraulic limestone, occurring in thick layers separated by thin 

 seams of dark and apparently carbonaceous matter. The waterlime 

 here shows a gradual transition from the Camillus. Fragments of 

 eurypterid heads and appendages are not uncommon, and frequently 

 Leperditia cf. alta, Whitfieldella laevis, and Leptostrophia varistriata 

 occur. Yet the marine' shells in both cases are seen to be of small 

 specific gravity such as would easily be floated in across mud flats, 

 and they evidently do not constitute a typical marine fauna since 

 too few forms are represented. These occurrences of two or three 

 species of brachiopods and of a crustacean in certain localities, far 

 from proving that the Bertie as a whole was deposited in the littoral 

 district of the sea, shows very clearly that the greater part of the 

 waterlime was not deposited in any part of the sea and that only at 

 intervals were a few marine organisms washed inland. Another sig- 

 nificant fact that has already been referred to in connection with mod- 

 ern deposits is the separation of marine and fluviatile faunas in dis- 

 tinct layers. When river water meets with the invading tide, the cur- 

 rent is checked and held back; this slack water is still fresh, and it 

 deposits its load of mud and organic remains above the reach of marine 

 waters. If marine currents later overcome the river currents and 

 pass up the stream channel, marine organic remains may be deposited 

 over the freshwater ones. Such lightweight structures as the exo- 

 skeletons of fluviatile Crustacea and other arthropods are probably sel- 

 dom carried out to sea against the opposing, denser salt water. If the 

 eurypterids were fluviatile, the occurrence of their remains in abun- 

 dance and well preserved in the regions where marine fossils are absent, 

 and their scattered occurrence in the localities where a few brachiopods 

 have been found is easily explained. Their entire absence from the 

 Rosendale waterlime and the appearance of only a single specimen 

 in the Rondout is likewise explained, since these deposits show a more 

 marine character than does the Bertie of the Buffalo and Herkimer 

 regions. The river portions of the Rondout and Rosendale either are 

 not uncovered or else have been removed by erosion. 



Summary. The only available source of the lime in the Bertie 

 is from the muds derived by the erosion of an older magnesian lime- 

 stone, the Niagaran, or in some cases, perhaps, the Trenton. Where 

 the Bertie is eurypterid-bearing, the rock was evidently deposited 

 above sea-level, as a river flood plain and subaerial delta deposit. 

 Southward and laterally the subaqueous part of the delta carries few 



