30 NEW YORK STATE MUSEUM 



process of deposition. Its irregular character is seen in the ledge 

 on the Grass river at Pollock's woods below Morley (locaLty S7')> 

 illustrated in plates 7 and 8. At the old mill site below Bucks 

 Bridge (locality 54) several inches of soft, deeply undercut shaly 

 layers are present at the contact, immediately followed by the rotten 

 fucoidal stuff. There seems reason to think, also, that the layers 

 making the base of the formation at some localities are not identical 

 with those at other localities, several feet of the lowest beds being 

 present or absent as the case may be. A similar difference in the 

 top of the Heuvelton below this contact has already been mentioned. 



Besides the localities marked on the map along the Heuvelton 

 contact (namely, 57', 55, 54, 38, 35, -28), these white basal layers 

 are exposed also in broad surfaces, the summit of a low, domed 

 uplift, east of Madrid depot (locality 7) near the north edge of 

 our quadrangle; and again similarly on the west bank of the 

 Raquette between Hewittville and Norwood (locality 22) mostly 

 just east of our limits. They appear also at and above the Hewitt- 

 ville upper dam (localities 26 and 27), and a mass of boulders of 

 this horizon occurs just south of Madrid (locality 9). 



The maximum thickness of these basal layers appears to be repre- 

 sented at Biucks Bridge in the beds of Nettle creek and the Grass 

 river (locality 55), where a hurried estimate indicated from 20 to 

 25 feet of cross-bedded, ripple-marked and sun-cracked, fucoidal, 

 partly calcareous sandy strata. Where these ledges cross the river, 

 making a considerable rapid (locality 54), gastropod shells of the 

 Ophileta type occur in them, especially at the old millrace on the 

 west bank (See figure B, plate 9). A good specimen from here bears, 

 according to Doctor Ruedemann, a considerable resemblance to Cle- 

 land's Pleurotomaria hunterensis^ of the Mohawk 

 valley Tribes Hill beds. Similar gastropods, though usually poorly 

 preserved and infrequent, characterize all levels of the Bucks Bridge 

 formation at practically all localities visited, and thus often furnish 

 a means of distinguishing isolated outcrops from those of the 

 Theresa. They appear to represent Vanuxem's Ophileta 

 c o m p 1 a n a t a,^ to which Cleland's species is probably equivalent. 



^ Bui. of Aimer. Paleontology, 3:252; pi. 17, fig. i, 2, 7, 8; ibid. 4:16; 

 pi. 4, fig. 1-2. According to U. S. Nat. Mus. Bui. 92, p. 1020, the present 

 name is Polygyrata hunterensis. But see the next footnote. 



