GEOLOGY OF THE POUGHKEEPSIE QUADRANGLE 49 



indistinctly followed to the river, where the limestone terminates in 

 a bluff. The northern portion of its eastern boundary is concealed 

 by drift, but farther south to the east of the road that runs south- 

 ward on the east of the driving park the limestone forms a con- 

 spicuous feature for several hundred yards along the eastern edge 

 of R. J. Kimlin's farm. Southwest from here it apparently follows 

 Casper creek to the Hudson river. The slates which come in 

 between it and the central strip form conspicuous ledges both north 

 and south of the Spackenkill road and were noted southwest of the 

 Poughkeepsie-Wappinger Falls road, on the east side of the road to 

 New Hamburg, and also near the Hudson river. The lower 

 reaches of Casper creek, west of the Poughkeepsie road, are choked 

 with kame deposits. 



Terranes present. The Potsdam and Trenton horizons have 

 been recognized in the strata composing this western strip of 

 limestone. 



The Potsdam. Fossils belonging to this horizon have been 

 discovered in a few places. The first were reported by Professor 

 W. B. Dwight^ from the northern portion of the strip. Just south 

 of the Poughkeepsie driving park, and to the west of the new pri- 

 vate road which runs south from the park to the Ruppert farm- 

 house, are a number of low-lying ledges. They have yielded: 

 ''Lingulepis pinniformis, L. minima, L. acumi- 

 nata, Obolella (Lingulella) prima, Obolella 

 . . . resembling 'n a n a,' Platyceras. Ptychoparia (Cono- 

 c e p h a 1 i t e s) n. sp. Dicellocephalus, Ptychaspis, Stromato- 

 cerium, encrinal columns." A few months later Professor Dwight 

 reported other Potsdam fossils from a locality about a mile 

 southeast by south on the Spackenkill road, about one-half mile 

 east of the Ruppert farmhouse, at the point wdiere the private 

 road to the Varick farm leaves the main road. In addition to 

 Lingulepis pinniformis and allied species found at the 

 first locality, he identified Ptychoparia saratogensis 

 Walcott, and P. calcifera Walcott.- These fossils may be 

 seen in the museum of the Vassar Brothers' Institute at Poughkeep- 

 sie. Another ledge yielding L. pinniformis was found by 

 Professor Dwight near the eastern margin of the belt about one-half 

 mile southeast of the first locality described.^ This ledge is just east 



1 Amer. Jour. Sci., Feb. i886, 31:125-37. See also Trans. Vassar Bros. 

 Inst., 4:130-41. 



2 Trans. Vassar Bros. Inst., v. 4, pt. 2, p. 206-14. 



3 Amer. Jour. Sci., July, 1887, 34 :28-32. 



