The Devonian Glenerie limestone outcrops throughout the Hudson Valley and is believed to correlate with the glauconite-rich Oriskany sandstone elsewhere in upstate New York. Field inspection of well-preserved outcrops in Rosendale, upstate New York, indicated the Glenerie formation to be composed of both thin and thickly-bedded chert, interbedded shale, and both calcareous to arenaceous limestone. The Glenerie formation is dominated by spirifer arenosis fossil, which is the index fossil for this formation. The goal of this research is to determine the conditions of the paleoenvironment prevalent to the deposition of the Glenerie formation. Within the arenaceous layers are the spirifer arenosis, Rensselaeria, and the Murchisoni fossils, which are shells that were deposited in a shallow marine environment. The calcareous layers are greatly affected by weathering and erosion that exposed fossils and trapped artifacts. The lithology of the area of focus, the inter-lake area of Rosendale, New York, encompasses formations of sedimentary strata ranging from Ordovician to the Devonian periods. The inter-lake area is severely faulted and folded, resulting from the continents of Europe and North America colliding. The Glenerie formation is bordered by the Port Ewen limestone to the east, and the Esopus shale to the west. The lithological and faunal content of the Glenerie formation changed as the depositional environment changed from shallow to deep water. The fossils indicated organisms with thick shells and presumably provided protection from being winnowed away in a shallow high energy marine environment. The preserved fossil record, along with bedded chert in the Glenerie formation suggest fluctuation in sea level followed by rapid burial of organisms.