132 
GEOLOGY OF THE THIRD DISTRICT. 
19. ONONDAGA LIMESTONE. 
Grey Sparry Limestone of the Reports. 
31. 
No. 1. Elongated pentamerus (P. elongata). Two views. No. 3. Undulated delthyris (D. undulatus). 
2. Consimilar hipparionix (H. consimilaris). 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 Icevis, 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 half 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. 
