CLINTON GROUP. 



27 



tf the others in very shallow water. In many instances, the marks of what appear to be wave- 

 lines are still preserved upon the surface of the layers. These markings have been regarded as 

 evidences of a line of beach at the period of the Medina sandstone, and the strata under con- 

 sideration follow in immediate succession to that period : they are, moreover, associated with 

 pebbly beds which were probably littoral. 



Some of these continuous tracks or trails I have been disposed to refer to the gasteropodous 

 mollusca ; but on comparison with such trails made upon recent beaches, they do not all appear 

 to have had such an origin, and there are likewise other animals which produce somewhat similar 

 tracks. Many of these markings resemble, in their tortuous direction, and in the manner of 

 crossing and recrossing the same line, the trails produced by the little Idotea upon the beaches 

 of our present coasts. Some of them, however, must have been made by animals of different 

 character. It is perhaps impossible to ascertain satisfactorily, at the present time, the origin of 

 all these singular and interesting markings ; but by calling attention to their existence in these 

 ancient strata, we may perhaps be able to find analogous markings upon our recent beaches. 



It should be noticed that all these markings are preserved in the arenaceous beds ; and though 

 they may have originally existed in the softer shaly beds, they would not now be visible. That 

 they have been sometimes made in the shaly layers, we have good evidence in the casts that are 

 often preserved on the lower side of the harder layers. The tracks or trails in question are always 

 seen upon the upper surface of the layers, and are not to be confounded with those curious and 

 variable markings so often found in relief upon the under sides of the harder layers, where they 

 rest upon shale. 



These markings occur in greater or less number and perfection throughout the entire extent 

 of the group, so far as I have been able to make examinations, but they are more perfect and 

 abundant in Herkimer and Oneida counties. The three characteristic varieties figured in the 

 plates have been found in a single locality. The condition of the strata is very variable, and 

 frequent alternations of shaly and arenaceous deposits are the characteristic features of this part 

 of the group. The mass here consists in its lower part of a coarse conglomerate with green shaly 

 matter intermixed, together with a bed of iron ore : still higher is a thick mass of shale, and 

 above this commence alternations of shale and thinbedded sandstones. It is in the latter that the 

 trails are most abundant and best preserved. 



PLATE XI. Figs, lab, tab, 3 & 4. 



Fig. 1 a, is a continuous trail, made by a single individual moving along a slightly elevated 

 ridge upon the surface of the sandstone. The trail continues along this ridge, often descending 

 slightly from the higher part, but always returning again, and recrossing itself many times in 

 succession. Beyond that portion of the stone figured, the trail leaves the ridge, crosses a slight 

 depression, which must have been more moist, or where water was still standing (as the trail is 

 very faintly perceptible), and again ascends to another elevated portion of the slab, where it 

 continues meandering about over a considerable space. 



