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 

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

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

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



1. Tubulifera: Corallum sclerodermal, tubular, without septa 

 oi % '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 Alcyonidce, doubtfully represented in the fossil state. 



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

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

 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 

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

 fossil Canadian representatives, unless the Graptolites, as inferred by 

 some palaeontologists, belong to this section. 



IV. 



ANTHOCORALLA OR ZOANTHARIA. 



The genera] 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 many Cainozoic and Mesozoic genera and species ; but Palseo- 



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

 on a preceding page. 



