108 ■ NEW YORK STATE MUSEUM 



The mean of four readings with the aneroid agrees well with 

 the total thickness here given. The beds of n'o. 1 have yielded 

 fossils at three points, all at about the same level near the middle 

 of the series, viz : one head of Eurypteyus remipes, and tolerably 

 abundant Leperditia alta, Nucleospira ventricosa and Meristella 

 hisulcata. 



Besides the irregularities in the bedding of no. 1 mentioned in 

 the section, the strata in this region are occasionally affected by 

 I'ocal disturbances. The most common of these is a sudden tilting 

 of the beds at a low angle, continuing sometimes a number of rods, 

 which is caused apparently by a failure of support from below. 

 One such disturbance occurs near the middle of no. 1, causing the 

 beds to dip very perceptibly to the southward for a short distance. 

 More considerable disturbances of a like character affect the 

 Corniferous limestones of Union Springs, about 2 miles south of 

 the plaster quarries, two of which have come under my notice. 

 One of these, which was mentioned and figured in the report of the 

 3d district, and by which the limestone is caused to pitch suddenly 

 south at an angle of 13°, has within the last two years been more 

 fully developed by the opening of a large quarry immediately 

 south of the disturbed beds. In this quarry, which is capped by 

 a considerable thickness of Marcellus shales with a band of con- 

 cretionary limestone, is revealed a flat-topped anticlinal arch with 

 an E. W. strike, the southern limit of which has not yet been 

 reached in quarrying, while the northward dipping side, with an 

 angle of 20°, is near the junction with the southward dipping beds 

 described by Yanuxem. In one of the most extensive plaster 

 quarries also, there occurs a gentle anticlinal with meridional 

 strike, through which the present working floor of this quarry 

 and the one to the north of it, is made to dip eastward at a small 

 angle as far as the workings extend ; and if this dip continues, it 

 will increase by a number of feet the space between nos. 2 and 4, 

 which was found by leveling to be 20 feet. The knowledge of these 

 occasional irregularities demanded caution in assigning the 

 gypseous series, with an average thickness of 25 feet, to its proper 

 place in the section, specially since the space of nearly a quarter 

 of a mile between the fossil-bearing beds of the lake shore and the 

 gypsum quarries, is concealed by drift. Fortunately the valley of 

 a brook, separated only by a single field from the nearest quarry 

 at this point, affords a continuous line 'of outcrop from the fossil- 

 iferous limestone on the lake to the top of no. 2, by which its con- 

 tinuity is assured. The top of no. 2 is 20 feet above the lake level, 

 which is also the hight of the floor of the nearest plaster quarry. 

 Add to this the fact that the character of no. 2 corresponds with 

 that of the bed of tough blue limestone which forms the bottom of 



