236 



MINERALS AND GEOLOGY 



zoic types are exceedingly rare, and fossil examples in our strata are 

 of very doubtful occurrence. Viewed broadly, the Class may be sub- 

 divided into four sections : Aporosa ; Perforata ; Sclerobasica ; and 

 Malacodermata. 



1. Aporosa : Tissues of the corallum ("sclerenchyme ") compara- 

 tively or essentially solid and compact. Includes the families of the 

 Turbinolidos, Astrceidce, Oculinidce, and Fungidce. No fossils in strata 

 of Central Canada. 



2. Perforata : Substance of the corallum essentially porous ; 

 cell-walls perforated. Includes the families of the Eupsammidce and 

 Poritidce (placing the Madreporidce with the latter). No fossils in 

 rocks of Central Canada. 



3. Sclerobasica : Corallum sclerobasal, horny or spicular ; Polyp- 

 tentacles simple, 6, 12, 18, or 24 in number. Includes properly 

 only one Family, that of the Antipathidce or so-called " black corals. " 

 No fossils. 



4. Malacodermata : No-corallum : entirely soft-bodied. Includes 



the Families of the Actinidce or 

 Zoantkifke. No fossils. 



sea anemonies," Ilyanthidce, and 



SUB-KINGDOM IV. 



ECHINODERMATA. 



The representatives of this division are marine, and, in the adult 

 state, typically radiated forms, with stomach distinctly separated 

 from the general body-cavity. The latter (with its system of appen- 

 dages, when present) is protected by an external calcareous test, 

 composed of numerous plates ; or otherwise, by a coriaceous integu- 

 ment strengthened by calcareous plates, tubercles, or spicula. In 

 some forms, the body is attached to the sea bottom, either per- 

 manently or during the earlier period of life, by a long or short stem 

 made up of numerous calcareous plates, mostly round or pentagonal 

 in shape, and perforated through the centre by a circular, stellate, 

 pentagonal or quadrate, orifice. The structural parts are almost in- 

 variably in fives cr multiples of five. In the more typical forms, 

 the test or skin carries numerous movable spines, whence the name 



