ON THE ECHINODERMATA. 
269 
chamber a Mediterranean species of fish—the Fierasfer—lives and 
luxuriates. Locomotion is effected by contractions and extensions of 
the body, and by action of the rows of tubular suckers. The 
British forms are grouped into five families, viz., i, P soli da; ii, 
Pentacta; ni,Thyones; iY,Synaptce; v, Sipwiadida. i 
Such, then, is an outline of the zoological portion of my subject. 
Let us now see what are the relations of these animals to the past 
history of our earth. Let me remind you that we divide the rocks 
forming the earth’s crust into Tertiary, Secondary, and Primary series, 
taking them in a descending order from the present unto the past, 
and each of these great divisions are formed of several groups. In the 
Tertiaries we have—1st, Lower or Eocene; 2nd, Middle or Miocene; 3rd, 
Upper or Pliocene; 4th, uppermost or pleistocene. In the Secondary— 
1st, the Cretaceous, or chalk formations ; 2nd, the Jurassic, or oolitic 
formations ; 3rd, the Triassic, or new red sandstone formations. In 
the Primary—1st, the Permian, or magnesian limestone; 2nd, 
Carboniferous, or coal hearing ; 3rd, Devonian, or old red sandstone ; 
4th, Silurian ; 5th, Cambrian ; 6th, Laurentian. Now most of these 
great rock groupings possess special forms of Echinodermata, the 
skeletons of which are found in a wonderful state of preservation, and 
capable of the most careful and minute examination. The specimens 
on the tables are sufficient to prove the correctness of this stateipent: 
therefore, when the naturalist comes to deal with these fossil forms he 
can speak with as much certainty anent their organisation as he can 
do of recent animals. 
I know of no class of the animal kingdom so well adapted for 
illustrating some of the laws which have governed the animalisation 
of the earth as the class we are now studying ; for the hard parts that 
we examine form an integral part of the organism, and reflect 
many of the leading features of their organisation. So that in 
examining the different groups of rocks we find that the Echinoderms 
of the one group entirely di:ffer from those of another, the generic 
forms are all perfectly distinct, and the specific characters of most 
of the species are quite unmistakable, so that an experienced 
palasontologist is capable of reading out a history of these rocks from 
the Echinoderms they are found to contain. 
The Grinoidea have played a very important part in the animalisa¬ 
tion of the globe, and the remains of their skeletons are strewn in 
great abundance. In some of the Palaeozoic and Mesozoic Rocks, they 
commenced their life-history in the Silurian epoch, and have peopled 
the bed of the sea with their varied forms through all subsequent 
epochs down to the present time. The Lower Silurian Rocks of North 
America afford a great many remarkable forms of Crinoids which are 
collected from the Chazy Trenton and Hudson River groups, but their 
numbers largely increase in the Upper Silurian beds. The Upper 
Silurian in the British Islands contains a very fine series. In the 
Upper Silurian Limestone of the Island of Gothland it is stated that 
