PORTAGE OH NDNDA GROUP. 



173 



and Genesee slate as dividing masses ; the Tully limestone, however, properly forming the 

 terminal portions of the lower part of the division, and the slate of the intervening one. 



From the information already given of this group, little more need be said, especially as it 

 is so greatly developed in the fourth district, and comes more appropriately under the head of 

 Ithaca group. 



As before said, its relative position is perfectly seen on Cayuga lake, and its general cha- 

 racters ascertained. The lowest layer on the lake is a sandstone, which the eye readily follows 

 south as it dips towards the water, resting immediately upon the Genesee slate. This layer 

 varies in thickness, in some parts being over a yard, and it is very compact and solid. The 

 under surface presents great numbers of those peculiar bodies, or fucoids, so common upon 

 the flagstones of the pavements of Ithaca, Homer, &c. They rise in relief upon the surface, 

 with their ends generally depressed, and are usually from one to two or more inches in length ; 

 their form somewhat quadrangular ; surface curved ; existing separately, or variously grouped 

 together and penetrating each other ; resembling the stiff simple markings, excepting as to 

 size, of the juvenile scholar. These bodies are not confined to this rock, but are found as 

 high as the top of the Inclined plane, but were rarely seen in a higher position in the series, 

 or even in a lower one. As yet the real nature of these bodies is doubtful, and they are there- 

 fore classed with Fucoids. The wood-cut at the head of this group will give some idea of 

 them ; but upon so small a scale, they are not so characteristic as upon a large one. 



Beside these fucoidal bodies, there are others upon the surface of the sandstone, throughout 

 the height of the group, which for the first time appear in the New- York system, but which 

 extend into the upper groups. They have the appearance of narrow-leaf grasses, broken into 

 fragments, and are invariably of a brownish black color. 



There is less of the hard sandstone layers on Cayuga lake than at Sherburne, the hard 

 coarse shale predominating west. 



44. 





1:11 



\ Hi 



I =° 



View of Buttress cliff, north of South point on Cayuga lake. From a Drawing by R. C. Tatloe. 



Along the lake shore from near South point, extending north for about two miles, the rocks 

 are of this kind, and form a highly picturesque cliff; their parts projecting in bold relief, caused 



