Oh. XXVI.] m UNITED STATES AND CANADA. 54.5 



sented by the upper part of what is termed " the Cliff Limestone." 

 There is a grand display of this calcareous formation at the falls or 

 rapids of the Ohio River at Louisville in Kentucky, where it much 

 resembles a modern coral-reef. A wide extent of surface is exposed 

 in a series of horizontal ledges, at all seasons when the water is not 

 high ; and, the softer parts of the stone having decomposed and wasted 

 away, the harder calcareous corals stand out in relief, their erect stems 

 sending out branches precisely as when they were living. Among 

 other species I observed single corals, not less than 5 feet in diameter, 

 of Favosites gotlilandica, with its beautiful honeycomb structure well 

 displayed, and, by the side of it, the Favistella, combining a simi- 

 lar honeycombed form with the star of the Astrcea. There was also 

 the cup-shaped Cyatlwphyllum, and the delicate network of the 

 Fe?iestella, and that elegant and well-known European species of fossil 

 called "the chain coral," Catenipora eschar vides (see fig. 631, p. 557), 

 with a profusion of others. These coralline forms were mingled with 

 the joints, stems, and occasionally the heads of lily encrinites. 

 Although hundreds of fine specimens have been detached from these 

 rocks to enrich the museums of Europe and America, another crop is 

 constantly working its way out, under the action of the stream, and 

 of the sun and rain in the warm season when the channel is laid dry. 

 The waters of the Ohio, when I visited the spot in April, 1846, were 

 more than 40 feet below their highest level, and 20 feet above their 

 lowest, so that large spaces of bare rock were exposed to view.* 



No less than 46 species of British Devonian corals are described m 

 the monograph published in 1853 by Messrs. M. Edwards and Jules 

 Haime (Palseontographical Society), and only six of these occur in 

 America ; a fact, observes Prof. E. Forbes, which, when we call to 

 mind the wide latitudinal range of the Anthozoa, has an important 

 bearing on the determination of the geography of the northern hemi- 

 sphere during the Devonian epoch. We must also remember that the 

 more conspicuous corals of these ancient reefs, viz., those which are 

 like our cup and star corals, all belong to the Zoantharia rugosa, a 

 sub-order which, as before stated (p. 515 et seq.), has no living repre- 

 sentative. Hence great caution must be used in admitting all induc- 

 tions drawn from the presence and forms of these zoophytes, respect- 

 ing the prevalence of a warm or tropical climate in high latitudes at 

 the time when they flourished — for such inductions, says Prof. E. 

 Forbes, have been founded "on the mistaking of analogies for 

 affinities." f 



This calcareous division also contains Goniatites, Spirifers, Pen- 

 tremites, and many other genera of Mollusca and Crinoidea, corre- 

 sponding to those which abound in the Devonian of Europe, and some 

 few of the forms are the same. But the difficulty of deciding on the 



* LyelFs Second Visit to the United States, vol. ii. p. 277. 

 f Geol. Quart. Journ., vol. x. p. 60, 1854. 

 35 



