106 



COELENTERATA CNIDARIA 



SUB- BRANCH II 



variety ; they occur either detached in the ectoderm and mesoderm, or are 

 closely packed together at the base to form a horny or calcareous axis (sclero- 

 basis), about which the polyps are distributed. Sometimes the calcareous 

 bodies (sclerodermites) form compact tubes which are periodically 

 partitioned off' into storeys with the upward growth of the 

 animal. Reproduction is accomplished either sexually or 

 asexually by basal or lateral gemmation, rarely by fission. 



Only the calcareous parts are known in the fossil state, such 

 as the solid axes, detached skeletal elements, tubes, and com- 

 posite coralla ; the horny structures are totally destroyed during 

 fossilisation. The Octocoralla make their appearance in the 

 Ordovician, but belong only exceptionally to the more common 

 fossils. 



I 



Family 1. Alcyonidae. Milne-Edwards and Haime. 



Fixed, fleshy, lobate, or ramose polyp stocks (very rarely simple 

 individuals), with echinulate or spicidar calcareous bodies (sclero- 

 dermites) occurring detached in the soft parts. 



Isolated sclerodermites readily escape observation, owing to 

 their minute size and fragile constitution. They have been 

 detected as yet only by Pocta l in the Upper Cretaceous strata 

 near Laun, Bohemia. 



Family 2. Pennatulidae. Milne-Edwards and Haime. 



Polyp stocks with base embedded in sand or mud, and with horny 

 or calcareous sclerobase ; polyps dimorphic. 



Slender, round, or quadrate calcareous axes referable to the 

 Pennatulidae have been detected with certainty only in the Trias 

 (Prographularia, Freeh.), Cretaceous (Pavonaria, Cuv. ; Pennatulites 

 and Palaeosceptron, Cocchi ; Glyptosceptron, Bohm), and Tertiary 

 (Graphularia, E. and H.), (Fig. 190). 



Family 3. G-orgonidae. Milne-Edwards and Haime. 



Fixed, branching, or fan-shaped colonies, with horny or calcareous 

 (Eocene) ! ime FarS solid sclerobase, or with jointed axis composed of alternating hoi-ny 

 and calcareous segments. 



FIG. 19t. 



Graphularia dcser- 

 torum, Zitt. Nuin- 



freh, Libyan 

 Desert, a, Axis, 

 natural size ; b, V , 

 Cross - sections ; c, 

 Striated surface, 

 enlarged. 



All the genera possessing horny, flexible axes (Goi'gonia, 

 Pihipidogorgio, etc.) are perishable. Detached remains referable 

 to Primnoa, Gorgonella, and Virgularw, the axes of which are 

 composed of both horny and calcareous layers, have been described from the 

 Tertiary. In the genus Isis the axis consists of cylindrical, calcareous segments 

 alternating with horny connecting joints. It is found fossil in the Tertiary, 

 and has been reported also from the Cretaceous. The genus Moltkia, occurring 

 in the Upper Cretaceous, has cylindrical joints which are pitted with slight 

 depressions indicating the position of branches. In the red or gem coral 

 (Gwallium, Lin.) the axis is built up of spiniform sclerites, which are united 



1 Pocta, PhilqU'- Sitzungsl.ericlite der Wiener Akatl. der Wisseiisch., Bd. 92, Jalirg. 1885. 



