las 



GEOLOGY or THE THIRD DISTRICT. 



19. ONONDAGA LIMESTONE. 

 Grey Sparry Limestone of the Reports. 



31. 



No. 1. Elongated pentameraa (P. elongate). Two Tiews. 

 2. Consimilar hipparionix (H. coasimilaris). 



No. 3. Undulated dellhyris (D. undulatus). 



4. Defensive fin bone of a fish (Ichthyodorulite). 



This limestone extends from the Helderberg to near Lake Erie. Its line of continuity is 

 unbroken in the third district, excepting by valleys or water courses. Though so persistent 

 as to direction and continuity, it rarely exceeds ten or fourteen feet in thickness. It is 

 readily recognized by its light grey color, crystalline structure, toughness, and its organic 

 remains, which are very numerous. It abounds in smooth encrinal stems, which for the pre- 

 sent may be termed Encrinites lavis, the largest species in the district, and is found only in 

 this rock in the State. Some of the stems are about an inch in diameter, and usually they 

 are over lialf an inch. In almost all its localities it is replaced by lamellar carbonate of lime. 

 Some of the specimens are in parts of a pink color, favorably contrasting with other parts 

 which are usually of a milk white color, and with the green shale of the rock to which its 

 layers and courses are owing. 



