642 



THE WONDERS OF GEOLOGY. Lect. VI. 



a temperature under 70°, and are therefore, with the excep- 

 tion of the Bermudas {ante, p. 614), restricted to inter- 

 tropical regions.* 



The simple turbinated corals, consisting, like the Fungia 

 (PL VI. fig. 8), of a solitary cell (Lign. 141, fig. 1. 3), 

 are found in great abundance and perfection in the Silurian 

 limestones of Dudley, Wenlock, &c. ; and are associated 

 with numerous large stony corals, and the elegant branched 

 Cyathophylla, Tubiporidae,t &c. Of the latter, the Wen- 

 lock limestone (in North America, as well as in England), 

 contains a genus of singular beauty, and which, from the 

 appearance presented by cross sections, is known by the 

 name of Chain-coral (Catenipora escharoides; Lign. 143, 

 fig. 3). The tubes of this coral being oval, and arranged 

 perpendicularly side by side in undulating lines, display in 

 the transverse sections elegant markings resembling the 

 anastomosings of delicate chains. 



The fossil branched polyparia, termed Lithodendron,± 

 form continuous layers, or reefs, in the mountain limestone 

 of Ireland ; and on the weathered surface of the stone, the 

 corals stand out in relief, as sharp as in the rocks of a 

 recent lagoon. 



The Syringopora3,§ which consist of clusters of parallel 

 tubes, laterally united like the recent Tubipore (PL V. fig. 

 9), prevail in many of the beds of mountain limestone, and 

 give rise to elegantly figured marbles (Lign. 143, fig. 2). 



36. Coralline Marbles. — Certain limestones, largely 

 composed of corals, in which the interstices have been 

 filled up by calcareous spar, and the inclosed zoophytes 



* See " Medals of Creation" for figures and descriptions of nume- 

 rous fossil corals, vol. i. chap. viii. 



f See the exquisite lithographs, 1>\ Mr. Scharf, in Sir 11. I. 

 Murchison's " Silurian System."' 



j " Medals of Creation," Lign. 55, pp.257, 303. 



§ Ibid. p. 297. 



