31 
Fig. 22.— Continued. 
Fig. 22: t/, Thecosmiha annularis. 
A few of the Asteroid corals may be found under the Creta- 
ceous, Case p, Sect, i ; and Endopachys Madurii and allied forms 
in the Eocene, Case p, Sect. io. Other forms may be seen in the 
European series, under the Jurassic. 
SUB-KINGDOM ECHINODERMATA. 
This group embraces the sea-urchins, star fishes and stone lilies, 
and is divided into the following five classes : Cystoidea, Crin- 
oii>EA, Blastoidea, Asteroidea and Echinoidea. The organ- 
isms are composed of many separate pieces or plates, and the 
divisions into groups are made upon the form and arrangement of 
these plates and the habits of the animals, which are all marine. 
CYSTOIDEA (Sack-like). 
These bodies are sack-like in general form, and are destitute of 
a true radial structure in the arrangement of their plates. The 
arms are usually sessile, small in size or obsolete, and the body 
either sessile or supported on a short stem. They are much less 
numerous, and less attractive in form, than the Critwidea. Ex- 
amples may be found under the Trenton group, in the Alcove 
Case, No. i ; in the Hudson River group (Agclacritius), Alcove 
Case, No. 2 ; in the Niagara group, Alcove Cases, Nos. 3 and 4 ; 
and under the Lower Helderberg group, Case r, Sect. 10. Caryo- 
