Pennsylvania Geology Final Report Volume 1 1981

198 GEOLOGICAL SURVEY OF PENNSYLVANIA.
fossil vertebrates of a higher order, reptilian or mammalian.
But whereas only three or four j^ears ago it was disputed
whether our Perry county Upper Silurian* fish spines and
plates (the oldest known to science) were not the spines and
plates of crustaceans, and whereas now true fish remains
have been found in the Lower Silurian (Ordovician) Tren-
ton limestone in the Rocky mountains,! it is easy to fancy
that cephalopod shells 'and ganoid tish may have lived
even in Cambrian times. As yet no air-breathing land animal
remains have been discovered in any rocks older than
the Carboniferous ; but, considering the extreme difficul-
ties attending their preservation, as compared with the easy
and safe burial of water animals, it is not at all a wild conjecture
that some sharp eye will light upon the traces of
their existence in earlier ages.:}: Only a few years ago the
Cambrian rocks were supposed to be non-fossiliferous. I
have inserted this chapter on Cambrian fossil life to guide
and stimulate students of geology in Pennsylvania, especi-
to a
cially the more youthful, curious and keen-sighted,
closer examination of our so-called "Azoic" or "No-life"
formations.
*See Claypole's discoveries in the Clinton formation No. V «. in Report F2.
f See C. D. Walcott's descriptions read at Washington, August, 189L
Jlf the discovery of a Silurian cockroach wing in Calvados, France, be
genuine, there was a Silurian world of land insects, and of course of land
animals to devour them. If Lesquereux was not mistaken about his fossil
Silurian land plants, there must have been land animals living upon their
fruit or foliage. In all ages foods have been followed (or accompanied) by
feeders. On the other hand, feeders presuppose foods. What did the Lower
Cambrian worms, polyps, shells and crustaceans live upon? Certainly not
upon mineral matter. Worms pass vast quantities of mineral matter
through their intestinal canal and leave it packed behind them in their burrows,
and this packing constitutes mostoi the "fossil cast." But they do this
in order to suck from the surface of the grains of sand and mud organic
matter which must have belonged to other creatures either alive or dead.
If alive, then microscopic animalcules. If dead, then the decomposed
tissues of other worms, sli ell-fish, etc., absorbed by the sand and mud.
But the first worms must have found living food. If the worms came first
and the polyps and mollusks afterwards, then the beginnings of life must
be conceived of as microscopic, cellular and vegetable ; in other words, an
Algoid or seaweed world, feeding on the chemical elements of the rocks
held in solution by the ocean water ; therefore casts of sea weeds in the oldest
rocks must be realities and not mechanical imitations.