94 Report of the State Geologist. 



4; Ludlowville shale. 



5. Encrinal limestone. 



6. Moscow shale. 



This follows the original division of the reports as regards 

 numbering, with a change of name for the first two, upon which 

 a few remarks are offered. 



{a) The Marcellus shale retains its character as a dark blue, fis- 

 sile, handsomely- jointed rock with Liorhynchus Umitaris, to the 

 top of its beds. The physical character of the shale changes 

 rather quickly to a lighter-colored and more calcareous shale, 

 with a substitution of the Hamilton series of fossils, which 

 becomes so decided as to leave no difficulty in the way of classify- 

 ing the stratum at six or eight feet above the Liorhynchus beds. 



{b) ^' A compact, calcareous blue shale, often passing into an 

 impure limestone." (Report of 4th Dist.) The designation 

 " basal limestone," proposed by J. JVI. Clarke for the strata as 

 observed by him in Ontario county (directly west for 25 miles) is 

 also of practical value for Seneca county. It fdrms a horizon not 

 easily overlooked by even the inexperienced, on account of its 

 physical contrast with the weak shales among which it occurs. 

 The rock thus designated is physically the same as the transition 

 shale, with increased power of cohesion, and a tendency to form 

 massive blocks, cleavable in clumsy chunks rather than laminse. 



As described in. Ontario county it is largely a coral reef. To 

 some extent it retains this character in Seneca county, displaying 

 scattered specimens of Heliophyllum, Favosites^ and other large 

 corals, which do not belong elsewhere near its horizon. Its quali- 

 ties as a material for road-making have been mentioned to me by 

 farmers. As a geographical factor it is of importance as causing 

 the first series of limitary cataracts, practically marking the com- 

 mencement of a geological series. 



Two such falls have been examined by the writer in the south 

 part of Geneva, in State Rock creek (25 feet fall) and Benton's 

 run (about 10 feet), thus connecting Clarke's observations with 

 the present set. 



In Seneca county seven exposures are noted, viz. : 



1. For half a mile along the shore of Seneca lake north of 

 Dey's Landing. One or two feet exposed. Impure, easily broken 



