museum: of comparative zoology. 



315 



north end of the Quarry Hill : they arc sandy limestones, without fossils 

 as far as observed, and not more than five or ten feet thick between char- 

 acteristic Hudson Eiver sandstones and shaly layers of the Waterlime. 



There is no distinction attempted on our map and sections between 

 the Waterlime and the Tcntacnlite hmestone : all the calcareous layers 

 below the knotted strata of the Lower Pentamerus are marked by a 

 single color. Professor Hail (Paleontology of New York, III.^ 386) 

 describes the Waterlime as being of " gray or drab-colored surface and 

 darker interior color, and almost destitute of fossils" ; while the Ten- 

 taculite is "a thinly bedded blue or black limestone, abounding in 

 certain organic remains." These characters are easily recognized. The 

 total thickness of seventy feet was measured on the eastern slope of the 

 Quarry Hill, from the uppermost sandstone to the lowest knotted lime- 

 stone. At Austin's Mills the measure would be less. The subdivisions 

 of the Tcntacnlite, as described at Kondout (see Lindsey and Dale, aa 

 below), arc here clearly made out. Some ten feet of fossilifcrous lime- 

 stone are followed by the Strumatopora layer, of one or two feet tbiek, 

 with numerous sponges a foot or a foot and a half in diameter (fig. 4) ; 

 next above come twelve feet of fine Pibbon limestone, in even parallel 

 layers, shown by alternating bands of lighter and darker color, often aa 

 thin as one twentieth of an Inch ; then comes the coarse Lower Penta- 

 merus, but about ten feet above its base thpre is a band of Eibbon 

 limestone again, one or two feet thick. The oven lines and smooth 

 gray weathered surface of the Ribbon limestone frequently serves as a 

 welhdetermined horizon, outcropping on the slope of the ridges made 



by the Lower Pentamerus. 



The fossils of the TentacuHte limestone commonly seen are a Leper- 

 ditia, a Tentaculiie, Orthis plicaia, and a Turritella (?), The first two are 

 very common on certain layers. The thickness of the Waterlime and 

 Tentaculite has already been mentioned as seventy feet or less. These 

 two divisions of the limestone group are well seen — at least their upper 

 members — at many points along the front of the Kalk Berg, around 

 the synclinal outlier opposite Austin's Mill, and at the head of tho 



southern anticlinal valley. 



Tho change to the coarse, heavy, knotted layers of the Lower Pen- 

 tamerus is accomplished within two or three feet. With this comes 

 tho frequent occurrence of dark chert iu irregular masses up to six 

 inches in diameter. The fossils easily found arc Fentainerus galeatm 

 (beaks arc very common on -weathered slopes in the soil) and Atry^ya 

 reticularis: both are common. The thickness measured about eighty 



