Geology of Sexeca Cou^'ty. 101 



stone in considerable quantities occurs after the first 100 feet ; 

 sparsely below. Kows of concretions occur at frequent intervals 

 in the cliff. 



The lower sections, as seen in Ontario county, exhibit a like 

 recurrence of material lithologically similar to the Genesee 

 shale — itself a recurrence of the Marcellus shale. As described 

 by J. M. Clarke they comprise, 1, green shales and a little 

 flagstone, 10 to 15 feet ; 2, black bituminous shales, the 

 "lower black band," about 40 feet; 3, greenish soft or sandy 

 shales with flags and many concretions, not less than 150 feet ; 

 4, black shales, 5 to 10 feet ; 5, flagstones and sandy shales, 150 

 feet. Above this lie 600 feet of heavy-bedded gray and greenish 

 sandstones, with some flags near the base. 



H. S. Williams estimates that the Portage fauna in the merid- 

 ian of Ithaca is distributed through approximately 1,300 feet of 

 strata. Clarke estimates the Portage rocks for Ontario county 

 at 600-700 feet. 



We may assume 1,200 feet as a large allowance for the thick- 

 ness of the Portage beds in the western part of Seneca county. 



Loxonema variety, with very fine ribs r 



Styliolina flssu rella, Hall co 



Buchiola retrostinata v. Buch o 



Palceoneilo muta. Hall o 



P. Bp. 



Lunulicardium fragile. Hall c 



Atrypa reticularis, Lin c 



Amhocoeliaumboyiata.B.&\\ c 



Spirifer like S. subumbona with minute, erect spinules on the concentric surface lines r 



Chonetea scitula, B.all o 



Ltorhynchus mesacostalis , Hall r 



Orthothetee, a small species occurring In the Portage fauna of the Naples section r 



OrWeutoidea, a very small form r 



Lingula spatulata, Hall o 



Cladochonus, a species occurring throughout the central New York sections at the base of the 



Portage ; in the Canandaigua lake section also in the Styliola limestone co 



After cart-ful examination Dr. Lincoln reports no evidence in Seneca county of the Styliola 

 limestone which seams to appear first in Yates county and extends thence westward nearly to Lake 

 Erie; a layer lying in the midst of the Genesee shales and containing many fossils which characterize 

 and herald the fauna of the Portage group. 

 The fauna of this Lodi limestone is especially to be noted for the following points : 

 It shows the incoming of a true Portage fauna (fauna with Goniatites intutnescens), as evinced by 

 Gon. Patersoni, Palceotrochus prcecursor, Loxonema Noe, Pleurotomaria capillaria, large form. 

 It also carries certain brachiopods which show the continued influences and presence of the Ithaca 

 fauna or eastern representative of the Portage group : Atrypa reticularis, Ltorhynchus mesacostalis, 

 Spirifer ct. subu7nbona, species which do not appear in the true Portage fauna. In view of the 

 earlier appearance of a concretionary limestone laj-er in the Genesee shales (Styliola limestone) 

 in more westerly meridional sections where the normal Portage fauna is developed, in which a true 

 Intumescens fauna appears, similar to that here noticed except in the absence of the certain 

 brachiopod elements, as well as the pre-eminent absence of calcareous layers from the arenaceous 

 Portage beds, I should be disposed to regard this layer as the final stratum of the Genesee division. 



J. M. CLARKE. 



