I 



CLAss III ALCYONARIA 109 



horizon (Tithonian) is especially characterised by their development. Reef 

 corals are also greatly developed in the Cutch (Jurassic) series of India. 



In the Lower Cretaceous (Neocomian) coral-reefs are found in France 

 (Haute -Marne and Yonne), Crimea and Mexico; while the Urgonian of 

 Switzerland and the Bavarian Alps is occasionally charged with corals. In the 

 Turonian and Senonian of the Alps (Gosau Beds), Pyrenees and the Provence, 

 numerous coral-reefs occur, usually accompanied by Budistae ; elsewhere, how- 

 ever, except in Holland (Maestricht) and Denmark (Faxoe), the Upper 

 Cretaceous contains but a limited number of reef-building Hexacoralla. 



In the older Tertiary (Eocene and Oligocene) occurrences of coral-reefs are 

 known on the northern and southern flanks of the Alps and Pyrenees, in Arabia, 

 India, the West Indies, and in Georgia, Florida, Alabama, Mexico and Central 

 America ; outside these areas their distribution is mostly sporadic. In the 

 Miocene and Pliocene the true coral-reefs retreat more and more towards the 

 equator (Red Sea, Java, Japan, Gulf of Mexico), while the Hexacoralla which 

 persist in geologic formations within the temperate zone (Vienna Basin, Italy, 

 Touraine) constitute but an insignificant feature of the general fauna. 



[Tlie foregoing sections on the Tetracorallä and Hexacoralla have been revised by Dr. T. 

 Wayland Vaughan, of the United States National Museum at Washington. It sliould be 

 observed tliat, in the present unsatisfactory state of our knowledge of these organisms, the 

 Classification adopted in this work, although perhaps as good as any available, is tentative in 

 character. — Editok.] 



Subclass 3. ALCYONARIA Milne Edwards. 



{Octacfinia Ehrenberg ; Oäocoralla Haeckel). 



Composite colonies, rarely simple polyps, the individuals provided with eight 

 mesenterial folds and eight broad, pinnately fringed, or plumose tentacles, which form 

 a Single cyde about the mouth, 



Hard skeletal elements are very generally developed in the Alcyonaria, being 

 absent in comparatively few forms, and are remarkable for their manifold 

 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 (sderodermites) 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 composite coralla ; the horny 

 structures are totally destroyed during fossilisation. The Alcyonaria make 

 their appearance in the Ordovician, but rarely occur in great abundance. 



Family 1. Alcyonidae Milne Edwards and Haime. 



Fixed, fleshy, lobate, or ramose polyp Stocks (very rarely simple individuals), with 

 echinulate or spicular calcareous bodies (sderodermites) occurring detached in the 

 soft parts. 



Isolated sderodermites readily escape Observation, owing to their minute 



