1062 NEW YORK STATE MUSEUM 



I 1 



The following species were obtained from the top layers of 

 the Becraft limestone: 



1 Monotrypa sphaerica (Hall) 



2 Leptaena rhomboidalis (Wilckens) 



3 Spirifer concinnus Hall 



4 Rhynchospira formosa Hall 



5 Eatonia medialis Vanuxem 



6 Gypidula pseudogaleata Hall 



7 S p i r i f e r sp. 



These form a transition to the Port Ewen fauna. 



Just above the stone-crusher quarry at Jonesburg an excava- 

 tion in the hillside shows the basal members of the Becraft. 

 The beds here are 6 inches to a foot in thickness, and separated 

 by shaly layers. The dip is 11° into the hill; the actual contact 

 is not exposed however. In the old Fred W. Jones quarry, 

 nearly the full thickness of the Becraft is shown in the quarry 

 face opposite the junction of the quarry road with the Jones- 

 burg cross road. About 6 or 8 feet of the lower beds are con- 

 cealed, which, together with the thickness exposed in the cliff, 

 about 35 feet, make a total thickness of between 40 and 45 feet 

 for the Becraft limestone. The Port Ewen appears a short dis- 

 tance south of the edge of the quarry, the surface slope here 

 being with the dip of the strata. Hence the above estimate of 

 the thickness is very close. A similar thickness of 45 feet was 

 obtained by measurement of the outcrop on the east side of the 

 mountain, where the strata stand vertically. The limestone has 

 been extensively quarried in the past for flux, the amount of 

 Ca Co 3 being nearly 92$. The following analyses were published 

 by Ries in his report, the Limestones of Neio York and their 



Econom ic Va hie. 1 



Lime 51.4 



Lime carbonate 91.7 



Carbon dioxid 49.191 



Magnesium carbonate 3.51 



Magnesia 2.233 



1 N. Y. State Geol. 17th An. Rep't 1897 ; N. Y. State Mus. 51st An. Rep't, 2 : 131 . 



