Geology of Seis^eca County. 91 



thin layers of flint in the upper part, near which was found Siy- 

 liola fissurella and a small variety of Ambocodia umbonata in 

 abundance. The lower part of the live feet was comparatively 

 firm, in part pyritiferous and with vermicular cavities. 



The geographical site of this exposure would refer it to the 

 lower layers of this formation. 



It seems desirable, in connection with this exposure, to place 

 on record those which lie in a direct line north of Geneva village, 

 comprising three quarries, as seen on the map. The northernmost 

 contains a tine exposure of the Onondaga limestone crowded 

 with many species of coral. The middle one is a close counterpart 

 of that at Waterloo falls, being a very black shale, varying from 

 heavy to fine, with Styliola and Ambocodia umbonata, small 

 variety, in near association. Other fossils hardly recognizable. 

 The lower layers become tough, retaining a tendency to split, and 

 at about fiYQ feet below the level of the above fossils it contains 

 various forms of Orthoceras and CyrtoceraSj including C. trivolve 

 (or undidatum, Conrad) ; not found elsewhere in Seneca county, 

 and lying below the Waterloo stream exposure. The southern 

 quarry presents nothing unusual. 



The system of quarry joints was nearly ^N". 25° W. and I^. 75° 

 E., with slight variations, and nearly vertical. The courses difi'er 

 in thickness, but maintain their individuality remarkably from 

 one quarry to another. 



The position of the courses is conveniently referred to an eight- 

 inch layer of light greenish gray material, called "marl" by 

 the workmen, which is constant ; it is found also at the Union 

 Springs quarry. It has somewhat the look but not the feel of 

 soapstone; breaks in -small flat, thick bits, and cuts easily. It is 

 not plastic. It is a nonhydrated aluminum silicate ; a clay, con- 

 taining small quantities of lime and magnesia. 



Besides the marl, there are one or two thin shaly bands ; and 

 a number of layers of hornstone, in part forming sheets of one to 

 six inches in thickness, in part separate nodules. 



Thin beds of a very small Zaphrentis and other small cup- 

 corals are found at different levels, well displayed by weathering 

 and forming good horizons for observation. Loxonema laxum of 

 an amber tinge is characteristic of certain levels. Chonetes 

 lineata ranges through most of the beds, in varying amount. 



