19 
Other specimens here shown are a section of Arietites, a mol- 
lusk allied to the modern nautilus, and tracks of reptiles of the 
Triassic period, on sandstone from Turner’s Falls, Mass. 
A model of the Moon is also exhibited here. This model 
in relief of the visible hemisphere of the Moon, is made on a 
horizontal scale of 1:600,000 and vertical scale of 1:200,000. 
The hemisphere is 18 feet in diameter. It is much the largest 
and most accurate work of the kind ever executed 
The division of the Moon’s surface into plains and moun- 
tainous regions is well illustrated, also the great size and pecu- 
liar characters of the volcanoes. 
HALL 35. 
This hall contains two somewhat distinct series, one intro- 
ductory to the study of fossils in general, the other, fossils of 
the Paleozoic era. 
Entering the hall from the West Court, the three wall 
cases on the right are those devoted to the introductory series. 
The first two of these are devoted to a comparison of ancient 
and modern forms. Beginning with the lower orders of life, 
there are shown sponges living at different periods of the earth’s 
history, and a modern sponge for comparison; while in succes- 
sion corals, crinoids, brachiopods, articulates and vertebrates 
are similarly illustrated. 
In the third case of the series methods of fossilization are 
illustrated. The methods shown include preservation of hard 
parts, as shells and bones, internal moulds, external moulds, 
impressions, incrustation, carbonization, silicification, phospha- 
tisation, etc. 
The wall cases to the left as the visitor enters from the 
West Court, and the floor cases, are devoted to fossils of the 
Paleozoic era. The order of these advances toward Hall 36, 
the floor cases being used for exhibiting the smaller fossils of 
each period illustrated by larger fossils in the adjoining wall 
case. 
Beginning with the Cambrian, several specimens of the 
Eozoon Canadense, supposed by some to represent the earliest 
form of life, are shown. 
