Anthozoa

ANTHOZOA.

In

this class of Polypes the tentacles are hollow, and, in most, with pectinated margins. The polypary is usually in ternal, and forms the bodies more properly called "corals and " madrepores." Asteroida.—Great doubt attaches to some of the fossils referred to this class of Polypi. The terms " Gorgonio." and " Alcyonium" have been applied to objects not well under stood, and usually proving to be Bryozoa and sponges. The Lower Silurian fossil called Pyritonema consists of a fasciculus of silicious fibres, and has been supposed to be related to the glass zoophyte (Hyalonema). The miocene deposits of Pied mont contain a species of the Mediterranean genus Coralliuni, an Antipathes, and an his (or Isisina, d'Orb.), which is also found in Malta. The London clay contains one coral (Graphu laria), referred to the Pennatulid,ce, and two Gorgonidts (Mop sea and Websteria).

Actinoida.—The lamelliferous or stony corals are (next to the Testacea) the largest and most important class of invertebrate fossils. They attained a great development in the earliest seas, and were perhaps more widely diffused and individually abundant in the Silurian age than at any subse quent period. " Reef-building" corals are now confined to warm seas, and are wanting even on great tracts of tropical coast. The Oculina is the only large coral now found in the north. But in palwozoic times the representatives of the modern Astrwas and Caryophyllias extended as far northward as Arctic voyagers have penetrated ; and at a much later period they formed reefs of considerable thickness and extent in the area of the coralline oolite. The Silurian limestone of Wenlock Edge is itself a coral reef thirty miles in length ; and the Plymouth limestone and carboniferous limestone have frequently the aspect of coral-banks skirting the older regions of Cambrian slate and Devonian " killas." The structure of coral-banks may be studied in the lofty limestone cliffs of Cheddar, and in the wave-worn shores of Lough Erne, as well as in the upheaved coral islands of the southern seas. In the fields about Steeple-Ashton, every stone turned up by the plough is a coral ; and our inland quarries and chalk-pith afford to the palaeontologist materials for the study of a class almost wholly wanting on the present sea-shores of Europe.

The history of the British fossil corals, as given by Milne Edwards and Haime in the " Monographs of the Palwonto graphical Society," exhibits, equally with that of the fossil shells by other authors, a transition from a state very different from that which now subsists in our part of the world, and a gradual approximation to the present order of things.

In the paheozoic 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 ter tiary genera and species resemble those of Southern Europe and our own coast.

The distinction between one large group of the palwozoic Actinoida (Cyathophyllid(r) and more modern corals consists in the quadripartite character of their plaited cups or stars, whereas the lamellae (or septa) of the other families are deve loped in multiples of 6. A remarkable exception exists in the Holocystis (fig. 5, s), 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 of by horizontal " tabulaen (fig. 4, 3), like the septa of the Nautilus and Spandylus. This character obtains not r. Amplexus Sowerbyi, Ph.; Carboniferous, Ireland.

2. Cyathophyllum turbinatum, Lin. ; U. Silurian, Wenluck.

3. Cyathophyllum subturbinatum (section); U. Silurian, Wenlock.

4. Cystiphyllum Siluriense, Lonsd. ; U. Silurian, Wenlock.

5. Zaphrentis Phillipsi, M. Edw. ; Carboniferous, Somerset.

6. Lithodendron irregulare, Ph. ; Carboniferous, Europe.

7. Lithostrotion striatum, Flem. ; Carboniferous, Europe. S. Acervularia luxurians, Eich. ; U. Silurian, Europe. 9. Heliolites interstincta, Wahl.; U. Silurian, Europe. o. Syringopora ramulosa, Goldf.; Carboniferous, Europe. r 1. Halysitea catenulatus, L. ; Silurian, Northern Regions. ix. Favosites Gothlandica, Lam.; Silurian, North.