100 C. U. Shepard on supposed Tadpole impressions 
tiously observes, “in concluding that the impressions were made 
by batrachians similar to those now living, I am by no means 
free from doubts as to the identity of the phenomena.”* The 
single figure he has givent+ (PI. L, fig. 1) of these markings, if 
taken by itself does certainly favor the hypothesis adopted; 
though it fails in its uninterruptedly smooth and continuous 
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depth. Occasionally also, unoccupied spaces are seen between 
the holes, whereas in the shale nothing is more striking than the 
general uniformity among the impressions, and the very com- 
plete manner in which the entire surface is covered by them,— 
raised lines (sometimes resembling swollen veins), being the only 
boundaries between contiguous cavities. 
The slabs of shale present three rather distinct varieties of 
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e second variety we have little more than the strongly 
nerved outlines of the hexagons. The cavity is shallow, oF 
nearly obsolete; but on its bottom, and proceeding from one 
and the same side relatively in each impression, is often seen 
tripartite, flame-like marking, or brush, which spreads over nearly — 
the area. The direction of this fan-shaped brush is con — 
stant throughout the series, thus evincing an origin from a com — 
mon cause, and one that acted simultaneously. The impressions — 
moreover are occasionally traversed by raised lines proceeding 4 
from a subjacent layer, and thereby subdivided into smaller com 
partments; but in these instances it is always easy to trace the 4 
hexagonal boundaries of the superior layer. The depressions — 
are obviously arranged in rows, somewhat approximating to fur 
* Ichnology of New England, 4to, 1858, p. 122. Boston. ¢ Idem. 
