MINERALS AND GEOLOGY OF CANADA. 511 
or more in length. Both occur in the Devonian series (Corniferous 
limestone (see Parr V.) of Western Canada. 
10. Cystiphyllum Senecaense (Billings) Fig. 81 (a Teer 
Corallum horn-shaped, simple, slender, and usually 
curved. Interior filled with vesicular tissue. Radia- 
ting lamellee quite rudimentary. Diameter three- 
fourths of an inch, to an inch and a half. Length, 
varying from three or four inches to two feet 
(Billings). Devonian rocks (corniferous limestone) 
of Canada West. Various other species of Cysti- 
phyllum occur in these rocks. Amongst others, C. 
aggregatum (Billings), in groups of irregularly 
cylindrical tubes covered by a wrinkled epitheca. 
Fig. 81. 
These corals represent our mostabundant and characteristic species, 
but numerous others occur in special localities. For information 
respecting many of these, the reader is referred to the Reports of Mr. 
Billings in the publications of the Canadian Geological Survey, and 
also to valuable memoirs by that paleontologist in the fourth and 
fifth volumes of the Canadian Journal. An extended analysis of these 
forms would not only exceed our proposed limits, but would be 
altogether out of place in an Essay like the present. 
AcaLerHa.—Until lately, this class was held to include only a 
series of soft-bodied marine animals (Meduse, &c.,) of which no fossil 
representatives have as yet been obtained. The recent researches of 
Professor Agassiz, however, render it very probable that the Graptolites 
and some of the lower forms usually classed amongst the corals may 
belong to this division. 
EcHINODERMATA.—The echinoderms constitute a class of marine 
animals provided with an external test or shell, composed of many 
pieces, or with a tegumentary semi-calcareous skin. Some are free, 
and others, fixed animals. These latter are attached to the sea-bottom 
by a jointed calcareous stem; but in some instances the animal is 
only thus attached during a portion of its life, and becomes free in 
the adult condition. The class may be subdivided into the following 
Orders: 1, Crinoida; 2, Blastoida; 4, Cystidea; 4, Thyroida; 5, 
Asterida; 6, Ophiurida; 7, Euryalida; 8, Echinida; 9, Holo- 
thurida. 
Vou. Vi. 2N 
