^7 
the present seas. They can be seen in Alcove Case, No. 9, and 
in Case m, Sects. 6 and 13. In the European series, Case R, 
several other forms of fossil sponges may be seen. 
Fig. 17. — Astylospongia prsemorsa Fig. 18. — Scyphia reticulata. 
CCELENTERATA. 
This sub-kingdom embraces a portion only of the animal forms 
formerly included under the old term radiata ; namely, the 
corals and coral-like animals ; and are divided into two groups or 
Classes, H vdroida and Zoantharia. Some authors of note also 
include Sponges, while others again class them with the Pro- 
tozoans. 
HYDROIDA. 
This group of animals are all aquatic; marine and fresh-water 
forms exist. They are mostly compound in their structure and 
increase by division or budding, and do not have the walls of the 
digestive sack separated from those of the general cavity of the 
body. Many of the jelly-fishes of our seas, the sea blubbers and 
sertularians or squirrel-tails of our beaches, and sea fans, belong 
to this class. They are represented among fossils principally by 
the Graptolites (stone-writings) in the lower and middle Paleozoic 
formations. Stromatoporas are also by some classed with them. 
The Graptolites may be seen in the Quebec group, Case b, Sect. 
7 and 8, and in the Utica slate, Case d, Sects, i and 2 ; in the 
Clinton group, Case d, Sect. 12 ; Niagara group, Case e, Sect. 3, 
under the name Dictyonema ; and also in the Potsdam (Dana's 
Manual series), Trenton, Upper Helderberg and Hamilton groups 
in single individuals. The general form of Graptolites may be 
understood from the following cuts, Fig. 19. 
