OF CENTRAL CANADA PART IV. 



235 



III. 

 CROSSOCORALLA OR ALCYONARIA. 



This division is composed largely of living forms. In these, the 

 polyps possess eight fringed tentacles, and there is a partial separa- 

 tion of the stomach from the general body-cavity. The corallum is 

 scleroderrnal or thecal in some forms, and sclerobasal in others.* 

 The Crossocoralla may be arranged under four Sections, (1), Tubuli- 

 fera ; (2), Spiculosa ; (3), Incellata ; (l),Pinnigera. 



1. Tubulifera : Corallum sclerodermal, tubular, without septa 

 or other internal structures. 



This section includes the living Tubipora or " Organ 

 Corals," and most probably the extinct (palaeozoic) Aulo- 

 pora. The latter genus is of not uncommon occurrence 

 in Canadian strata. Figure 149 represents a Devonian 

 form. 



2. Spiculosa : Corallum slerodermal, coriaceous, with 

 imbedded calcareous, branching, spicula; fixed. Includes 

 the Alcyonidoe, doubtfully represented in the fossil state. 



3. Incellata : Corallum sclerobasal, horny or calcareous ; fixed. 

 Includes the Gorgonidce, or " sea fans," the Isidacece, and the Corallidce 

 the latter represented by the well-known " Red Coral " of the 

 Mediterranean and Red Sea. No fossil representatives in Canadian 

 strata. 



4. Pinnigera : Corallum sclerobasal, horny ; free. Includes the 

 Pennatulidce, or "sea pens" Pennatula, Renilla, Virgularia. No 

 fossil Canadian representatives, unless the Graptolites, as inferred by 

 some palaeontologists, belong to this section. 



FIG. 149. 

 Aulopora cor- 



IV. 

 ANTHOCORALLA OR ZOANTHARIA. 



The general absence of tabulae, and the typically hexamerous 

 character of the radiating septa, are the leading characters of this 

 class. The Anthocoralla include a great number of existing corals 

 and manv Cainozoic and Mesozoic genera and species ; but Palaeo- 



* See explanation of these terms in the introductory remarks prefixed to the Hydrocoralla 

 on a preceding page. 



