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 (selero- 
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. 

Family 1. Alecyonidae. Milne-Edwards and Haime. 

Fixed, fleshy, lobate, or ramose polyp stocks (very rarely simple 
individuals), with echinulate or spicular calcareous bodies (sclero- 
dernutes) 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 Potta 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, Frech.), Cretaceous (Pavonaria, Cuv. ; Pennatulites 
and Palaeosceptron, Cocchi ; Glyptosceptron, Bohm), and Tertiary 
(Graphularia, E. and H.), (Fig. 190). 


b 
Fic. 190. Family 3. Gorgonidae. Milne-Edwards and Haime. 
Graphularia deser- “ ; 7 7 
torum, Zitt. Num- Fixed, branching, or fan-shaped colonies, with horny or calcareous 
litie limest F at tae ; hs 
miececey aw Wate solid sclerobase, or with jointed axis composed of alternating horny 
eae nein and calcareous segments. 
aS rae . All the genera possessing horny, flexible axes (Gorgonia, 
Striated Surface, Phipidogorgia, etc.) are perishable. Detached remains referable 
‘ Primnoa, Gorgonella, and Virgularia, the axes of which are 
composed of both horny and calcareous layers, have been described from the 
Tertiary. In the genus Jsis the axis consists of cylindrical, calcareous segments 
alternating with horny connecting joints. It is found fossil in the Tertiary, 
and has heen repor ted also from ie 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 
(Corallium, Lin.) the axis is built up of spiniform sclerites, which are united 
1 Potta, Philipp, Sitzungsberichte der Wiener Akad. der Wissensch., Bd. 92, Jabrg. 1885. 
