O. C. Marsh on a new species of Protichnites. 47 
CIT eee ee eee 
the geological age of the strata containing them was fully dis- 
cussed by Sir Wn. E. Lo an, and a more detailed description 
of the footprints was given by Prof. Owen, who now regarded 
them as made by a large ebdbenete, probably allied to the mod- 
ern Limulus.* He applied to these impressions the generic 
name Protichnites, and distinguished six species, or varieties, 
apparently quite distinct from each other. + A trail of a different 
character was afterwards discovered in the same formation, near 
Perth, Canada West, and described by Sir Wm. E. Logan, un- 
der the name Olimactichnites Wilsoni. t This was supposed 
to be the track of a Gasteropod, but Prof. Dana has since sug- 
gested that it may have been made by a large Trilobite.§ Up 
to the present time, eight localities of footprints have been found 
in the Potsdam sandstone of Canada, along the strike of the 
formation for about 400 miles, and all at about the same hori- 
zon, or within 50 to 70 feet of the top. 
From the Lower Silurian of the United States, no footprints 
appear to have been described hitherto, although their existence 
in these strata is now clearly esta lished. Aw interes ting series 
of impressions was discovered by the writer on the western shore 
Se me Fst 
Fa Tee ee Se ee en i eee 
_ hard, white quartzite, eae that containing the Dotan 
in Canada, although probably roan, to a somewhat lower 
orizon, The impressions obtained, which indicate a new form 
_ of Crustacean track, were in two portions, ot the same surface, 
_ and evidently made by the same animal. They form together 
a series of footprints, about six feet in length, consisting of 
two parallel rows of impressions, separated from each other by 
a space of about one and three fourth inches, and having an 
Pach an impression can be detected, even when the track passes 
over the Pi gee of the ripplemarks, where it certainly would be 
_ * This opinion has since been confirmed by Dr. J. W. Dawson, after an exami- 
4 0g of the prairie of a living specimen of L. polyphemus. Canadian Natural- 
uralist, Vv, p. 2 
i, p- 
t Joaraal of “ee Geological hog i. pace viii, pp. 199 and 214. 
Canadian 
Manual of Gecoey, p. 189, i douieey of Canada, 1863, p. 108. 
