ANTHOZOA. 25 



the world, and a gradual approximation to the present order 

 of things. 



In the palaeozoic strata the corals belong chiefly to two 

 extinct orders ; those of the secondary period more resemble 

 living corals of warmer climates than ours; and the few 

 tertiary genera and species resemble those of Southern 

 Europe and our own coast. 



One large group (Cyathopliyllidce) of palaeozoic corals 

 presents a quadripartite character of the plaited cups or 

 stars ; whereas the lamellae of the polype-cells of later and 

 modern families of Anthozoa are developed in multiples 

 of 6. A remarkable exception, however, exists in the 

 Holocystis (fig. 5, 8), an Astrea-like coral with quadripartite 

 stars, which is found in the lower greensand. The old-rock 

 corals are also remarkable for the manner in which they are 

 partitioned off by horizontal "tabulae" (fig. 4, 3), like the septa 

 of the Nautilus and Spondylus. This character obtains not 

 only in the Cyatliophylliclce, but also in the Milleporidce, Favo- 

 sitidce, and other palaeozoic families. Of the 129 Silurian 

 corals, 121 belong to the tabulated divisions. 



The Devonian system contains about 150 described corals, 

 the carboniferous limestone 76, and the magnesian limestone 

 only 5 or 6. The commonest forms of simple, turbinated 

 corals, are Cyxthophyllum (fig. 4, 2 and 3), which exhibits four 

 slight fossulce in its cup, and is often supported by root-like 

 processes. In Zcuphrerdis (fig. 4, 5), there is but one deep 

 fossula. Am/plexus (fig. 4, 1) is a characteristic carboniferous 

 fossil, nearly cylindrical, and often so strait and regular in 

 its growth as to have been originally described as a chambered 

 shell. The radiating septa are very slight, and the horizontal 

 partitions simple, flat, and almost as regular as the septa of 

 the Orthoceras. In the Silurian Cystiphyllum (fig. 4, 4) the 

 lamellae are also evanescent ; but the tabulce are represented 

 by numerous vesicular plates. The corals of these genera are 



