30 



»ALiOKTOLOGT or NEW. YORK. 



PLATE XII. Fig. 4. 



This figure is from the surface of a large slab, marked by these meandering tracks. These, m 

 their general aspect, are similar to those preceding ; but they present, in addition, fimbriated or 

 ciliated margins, which, although not very distinct in these specimens, are nevertheless absolute 

 and important features. In some portions of the same track, this character is scarcely or not at 

 all visible, while in other parts they are sharp and well defined markings. 



Tracks of this character are not so abundant as the preceding kinds, but they are neverthe- 

 less frequently found intermingled with them upon the same slab. 



Position and localily. Blackstone's quarry, New-Hartford. 



PLATE Xm. Figs. 1 a, b, c, d; and fig. 2. 



All the figures upon this plate are of one type, though differing to some extent among them- 

 selves. The peculiar feature of the preceding ones on Plate xi, of having a depression at each 

 side, with an elevated ridge in the centre, is not here so characteristic. Most of them, indeed, 

 appear to be only a single continuous fimbriated depression, gradually rising from the centre 

 towards the margin, where a slight ridge is formed, elevated above the surface of the surrounding 

 stone. 



The central ridge which exists in some of these trsdls appears not to have been an original 

 feature, but to have been caused by a partial filling up of the fimbriated trail. The trails of this 

 character show a deeper depression along the central line than the marginal depressions in the 

 other species, as if the bodies making them were heavier, or rested upon a less extent of surface. 



Fig. 1 a represents a part of the surface of a slab, marked by these fimbriated tracks. The 

 trail from e to e' is clearly the oldest or first made trail, since it is crossed by the two others at 

 m and p. The trail o' o was subsequently made, crossing the one e e' at p ; and again the third 

 line was made from e" to e"', which crosses both the preceding ones. Between e and e^', the 

 meeting of the two trails is very obscure, and they appear like one continuous trail : they are 

 distinct, however, though perhaps made by the same animal. 



The crossing of these trails affords a clue to the direction in which the animal moved ; and 

 it appears to have been from c to e', and from e" to e"'. The crossing at m shows that the animal 

 moved from e" to e"', since the marginal ridge of the trail crossed is pressed onward in the same 

 direction. Again, in the crossing at n, the mar^s of the trail o o' are pushed forward in the 

 direction of e"'. 



The trail from e to e', first made, was probably continued beyond e" ; and, after turning 

 to the right beyond the margin of the specimen, comes again upon the same slab at e", re- 

 crossing the same trail twice before leaving the slab. During this interval, another similar animal 

 had crossed from & to o. These trails throughout present no elevation in the centre. 



Fig. 1 6. A trail similar to the last, but which appears to have been partially filled by the 

 flowing in of mud. 



