1879. | Columbia College. 505 
numerous trilobites, with the Eurypterus, Pterygotus, etc., show 
us that the Crustaceans were the highest form of life on our 
continent during the Silurian age. But while the Crustaceans 
were the highest in point of structure, yet they were far in- 
ferior in size and strength to the Cephalopods, the highest 
of the Mollusks, which lived in the same seas. These were re- 
presented by huge Orthoceratites. As we stand beside the cases 
containing these beautifully preserved remains, it is not difficult to 
restore them once more in fancy to the ancient waters in which 
they lived, and to picture to ourselves the appearance of the earth 
in that distant age. All the remains of animal life which these cases 
contain are those of marine forms. All the remains of plants, 
too, discovered in the rocks of this age have been classed with 
the Algæ (or sea-weeds). Judging from the fossil records, which, 
however, we feel are incomplete, we conclude that no plants grew 
upon the Silurian land areas! There was then but the broad 
ocean and the wild desolate shores, uninhabited by beast, or bird, 
or plant—even more dreary and silent than are now the barrenest 
islands of the southern oceans. Along these primeval shores the 
waves rolled in and ground away the rocks as they do on the 
Coast to-day, and retreating left the sands with a ripple-marked 
Surface or covered with the trails of worms and crustaceans, 
Many of the shell-fish and trilobites lived along the shore, per- 
haps sheltered by clumps of sea-weed and clinging brachiopods, 
others inhabited deeper waters and contributed their remains to 
the formation of the limestone in which we now find them. 
With this imperfect glimpse of our country in the Silurian 
times, we must pass on to the fauna and flora of the next succeed- 
ing, Devonian, age. Again naming the era from the ruling 
forms of life, we call this the age of fishes. Although in: Europe 
the first fishes made their appearance in the preceding age, yet in 
Our country we find their earliest remains in the Devonian rocks, 
throughout which time they continued to be the highest forms of 
life on the globe. What at once strikes the observer upon 
glancing over the splendid display of Devonian fossils here 
brought together, is the almost total absence of the forms with 
which we have already become familiar in the Silurian. Here 
begins a new chapter in the ancient archives. The few inches 
1 Since this was written a number of species of land plants have been described 
from the Silurian rocks of our country by Mr. Leo Lesquereux. 
nat 
y 
Sr 
