V2 FIELD MUSEUM OF NATURAL FIISTORY 
where they occur, are thus placed first; then in order, Pro- 
tozoans, Radiates, Molluscs, Articulates, and Vertebrates. 
The specimen labels show: 1st, the name of the species and 
that of the authority by whom named; 2d, the geological period 
or epoch to which each belongs; and 3d, the locality. 
Alcove 103. 
Here are shown several large specimens of general geological 
interest. Among them are two broad slabs of rock cut from 
ledges the surfaces of which had been scoured and polished by 
movement of the continental glacier over them. One of the 
slabs is sandstone from North Amherst, Ohio; the other is lime- 
stone from Kelley’s Island, Lake Erie. Several types of glacial 
marking are illustrated on the slabs, including fluting and ice- 
berg action. The slabs are probably the finest of the kind to be 
seen in any museum. Other specimens here shown are a section 
of Arietites, a huge mollusc 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 is a model 
in relief of the visible hemisphere of the Moon, 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 pecul- 
iar forms of its so-called volcanoes. 
Hall 33. 
This hall is devoted to fossils of the Paleozoic era and the 
Triassic period of the Mesozoic era. The series begins at the 
south end of the hall with the Cambrian period and continues 
toward the north end with the Ordovician, Silurian, Devonian, 
Mississippian, Pennsylvanian, Permian, and Triassic in the order 
named. 
Cambrian Period . — The Cambrian is the earliest period from 
which well-defined fossils are known, and many of these are frag- 
mentary and rather obscure. Eozdon canadense, of which several 
specimens are shown, is found in rocks older than the Cambrian 
