88 
THE FERN FORESTS OF 
which seeks a moist atmosphere, or whose larvas 
live altogether in water. They are not usually 
well preserved, as will be seen from the broken 
character of the one here represented, although 
the wood-cut is made from a better specimen 
than is often found. We have, however, re- 
mains enough to establish unquestionably the 
fact of their existence in the Carboniferous pe- 
riod, and to show us that the type of Articulates 
was already represented by all its classes. 
Not so with the Vertebrates. Fishes abound, 
but their class still consists, as before, of the Ga- 
noids, those fishes of the earlier periods built on 
the Gar-Pike and Sturgeon pattern, and the Sela- 
chians, represented now by Sharks and Skates. 
In the Carboniferous period we begin to find per- 
fectly preserved specimens of the Ganoids, and 
the adjoining 
wood-cut rep- 
resents such a 
one. Of the 
old type of 
Selachians we 
have again one 
lingering representative in our own times to give 
us the clew to its ancestors, — as the Gar-Pike 
explains the old Ganoids, and the Chambered 
Nautilus helps us to understand the Chambered 
Shells of past times. The so-called Port-Jaekson 
