132 
THE GEOLOGIST. 
of fossil tracks with some good results, is to be lound iu Prof. Em- 
mons's 'American Geology,' part vi., 1857, chap, xvi., p. 135, etc. 
Eeferring to the fossil tracks found so abundantly in the sandstone 
of the Connecticut Valley, he says : — " In the progress of discovery 
other imprints have come to light, differing in every respect from the 
preceding. Those in the first instance were regarded as fossil Ne- 
reites, Myrianthes, etc., or Annelids, whose surfaces, or exterior, 
possessed a sufficient consistency to form an imprint upon a yielding 
surface. Most of these markings, however, are now referred to foot- 
er body-marks of Crustacea or Mollusca, which have been made in a 
manner similar to the trails of certain shell-fish, as they move over a 
soft bottom. Such trails are preserved upon the rocks ; but in addi- 
tion to these, there are many others which must be due to water- 
insects, or their larvae. We may easily convince ourselves of the 
possibility of the preservation of footprints, or the trails of the bodies 
of larvso, by the inspection of a pool of water which has stood a few 
days after a shower of rain. These pools, Mhile drying, will leave 
frequently a smooth, glossy surface of indurated clay or mud, which 
will be marked by innumerable tortuous 
lines of different patterns, according to the 
character of the body and feet possessed by 
the animal which has travelled over this 
smooth impressible surface. 
" As these recent trails are instructive as 
well as useful in explaining ancient pheno- 
mena of a similar kind, I propose to illus- 
trate their characters by the annexed figures 
of some of the more common form of trails 
which may be seen by the margins of drying 
pools of water during the suuuner season. 
Fig. 105 (fig. 3) is a copy of the imprints 
made by the larvae of two diflPerent species 
of dipterous insects. It is, however, only 
of the larger that I can speak with cer- 
tainty ; for I have found in this trail, or by it, the dead larva. The 
darker spots which terminate the finer trail mark the places M'here 
the larva entered the mud. Frequently 
the larger trail terminates in a hole in 
the mud also. Fig. 106 (fig. 4) is copied 
from another pattern, having lateral 
fringes. This resembles very closely the 
imprints which have been referred to Ne- 
reites. Upon this surface, also, the im- 
pressions of rain-drops are perfectly pre- 
served. 
" An equally interesting kind of trail 
is exhibited in the margin (fig. 107), , ,,,, 
which was probably made by a water' ^ 
insect, or one having legs (fig. 5). The first (fig. 105) were made by 
Fig. 3 (105, Emmons). 
