NIAGARAN (aNTICOSTIAN) SERIES 713 



For the present it can only be stated with some degree of probability 

 that the Clinton faunas begin to appear in the lower Gnn Eiver forma- 

 tion and then continue throughout the Jupiter Eiver division, and grad- 

 ually take on more and more of the characters of the Irondequoit or 

 highest reef Clinton, an aspect which is not fully attained even at the top 

 of Division E, where Anoplotheca hemispherica is in greatest develop- 

 ment. If, on the other hand, one uses the occurrence of Monograptus 

 clintonensis and Spirifer radiatus meta as the guide for correlation, then 

 the higher Clinton of New York and the northern Appalachians holds 

 the time of the higher zones of the Jupiter Eiver formation — that is, 

 from Eg to Eg. It is therefore concluded that the New York Clinton 

 begins later than the lower half of the Gun Eiver and that the higher 

 Clinton (Williamson and Irondequoit) correlates best with the zones 

 above Eg of the Jupiter Eiver formation. 



Jupiter River formation (Richardson's Division E). — The strata of 

 this formation are best seen beginning at the high cliff on the west side 

 of Jupiter Eiver (hence the name for the division) and thence eastward 

 to the Jumpers. The thickness of these beds is 561 feet, which in the 

 main are thin-bedded light colored limestones interstratified with shale 

 partings. The lower 100 feet are green shales followed by a similar 

 thickness of argillaceous limestones above which the limestones are purer. 

 'No intraformational conglomerates were seen in this formation. 



The formation is again seen along the southeastern shore of the island 

 from Heath Point westward to Pavilion Eiver. These deposits are prob- 

 ably those of somewhat deeper and certainly of clearer water, with fairly 

 uniform physical conditions, seen in the fact that the strata here are 

 more uniformly limestones in which corals, coral reefs, and large brachio- 

 pods (Pentamerus ohlongus chiefly) abound. The thickness of these 

 eastern Jupiter Eiver equivalents has not been ascertained. The strata 

 are nearly horizontal and undulating. It is believed^ however, that their 

 thickness fully equals that of the western exposure. 



According to Eichardson's section the zones along the southwestern 

 shore of the island are as follows : 

 Triplecia ortoni heds — continued. P^^^. 



El. Not seen 27 



Ea. Light green argillaceous shales. Finely exposed in the lower part 

 of West Cliff of Jupiter River. Only fossil seen is Atrypa 

 reticularis. Richardson's estimate of thickness is 60 feet, the 

 authors' 80 



Eg. Light drab argillaceous limestones. Strata much jointed, in which 

 the fossils are often excellent, but scarce. They are Mono- 



