140 PALEONTOLOGY OP NEW-YORK 



CHONETES OF THE CHEMUNG GROUP. 



In certain localities of the Chemung group, within the State of New- 

 York, there are numerous specimens of Chonetes ; but they occur in the 

 condition of casts of the interior, or of impressions of the exterior of the 

 shell. The strata containing them present all the phases of argillaceous and 

 arenaceous admixtures, sometimes a soft evenly laminated shale, and 

 Bometimes a coarse ferruginous sandstone. The fossils therefore present 

 a great variety of aspect, and very different degrees of perfection and of 

 prominence in the characteristic markings. 



This condition, moreover, renders it the more difficult to make satis- 

 factory comparisons with specimens retaining the shell, and occurring 

 in other kinds of sediment. Notwithstanding these difficulties, I have, 

 after much labor, satisfied myself that the greater part of all the speci- 

 mens found in the Chemung group may be referred to three of the forms 

 described from the Hamilton group : these are C. scitula, C. lepida and 

 C. setigera. The two former, which I have sometimes been disposed to 

 regard as perhaps identical species, maintain in the Chemung group the 

 same differences that they show in the Hamilton group. There are a few 

 obscure remains which do not appear referable to the preceding, having 

 more numerous striae than C. scitula and approaching in character C. 

 illinoisensis. 



In the higher strata of the Chemung group in Chautauqua county, and 

 in similar beds at Meadville, Pa., a very marked and distinct species of 

 Chonetes has been found. In its larger examples it equals in size and 

 has the general form of C. coronata of the Hamilton group, but is readily 

 distinguished by having a truncate apex and the surface studded with 

 Blender spines. 



In extending our researches beyond the limits of the State of New- 

 York, we find in the shales and sandstones of Eastern Ohio (which in 

 part I regard as representing the Chemung group), one or two species 

 not known in New- York : these, however, are associated with the C/io- 



