90 
THE FERN FORESTS OF 
There were a great variety of the Selachians 
in the Carboniferous period. The wood-cuts be- 
low represent a tooth and a spine from one of the 
most characteristic groups, but I 
have not thought it worth while 
to enumerate or to figure others 
here, for there are no perfect spe- 
cimens, and their structural dif- 
ferences consist chiefly in the 
various form and appearance of 
the teeth, scales, and spines, and would be unin- 
teresting to most of my readers. I would refer 
the more scientific ones, who may care to know 
something of these details, to my investigations 
on Fossil Fishes, published many years since 
under the title of “ Recherch.es sur les Poissons 
Fossiles.” 
Although the Vertebrate division of the Ani- 
mal Kingdom still waited for its higher classes, 
yet it had received one important addition since 
