30 
There will also be found here a collection of local fossils, 
gathered from the Niagara beds of Northern Illinois. 
Case 1 A, Hall 35.— Fossils of the Laurentian period. The 
only fossil illustrating this period is the problematic Eozoon Can- 
adense, several specimens of which are shown. It is thought by 
some to represent the fossil remains of a gigantic Rhizopod, but is 
generally considered to be of wholly inorganic origin. 
The remainder of Case 1 and Cases 2 A.-F.— Fossils 
of the Silurian age or age of Invertebrates. The life of this age is 
almost wholly marine and made up chiefly of corals, crinoids, 
brachiopods and mollusks. It is illustrated in the collection ac- 
cording to periods as follows: 
Case 1 A and B.— Cambrian and early Silurian fossils. Old- 
hamia — probably a plant of the order of marine algae. Brachio- 
spongia — a representative of the class of sponges. Monticiilipora 
— of Corals. 
Diplograptiis, Tetragraptus — Hydroids known as graptolites 
— abundant fossils of this era. The name is derived from the Greek 
word meaning “to write” and refers to the plume-like nature of 
their remains. Scolithus — supposed to represent the borings and 
tracks of worms. 
Tentaculites—vmmx\^ mollusks of the class of Pteropods. 
Conularia — perhaps also Pteropods. 
Paradoxides, Asaphus, Olenellus, Agnostus—T rilobitts, the 
most common and characteristic fossils of early Silurian times. 
They were crustaceans, allied to the horse-shoe or king crabs of 
the present day. Two models illustrate the various parts of their 
structure, and tracks of a trilobite, genus Climatichnites, are shown 
on a large slab of sandstone from Wisconsin. The number of 
great animal types having existence in even the earliest geological 
periods is worthy of note. 
Between Cases i and 2 , a cast of an Orthoceras, nine feet in 
length. This shows the size which these Cephalopods, repre- 
sented at the present time by the Nautilus, attained in early times. 
They were a striking feature of the Palaeozoic era. 
Case 2 A. — Trenton and Cincinnati epochs. ReceptaculiteSt 
Selenoides — probably calcareous sponges. Favistella — Corals be- 
longing to the family Favositidae or honey-comb corals, so called 
