342 



THE GEOLOGIST. 



In the Devonian deposits throughout the world about one hundred 

 and fifty species of fossil corals have been found, forty-nine of which 

 occur in Devon and Cornwall. Twenty-three of these are found in 

 continental Europe, and six in America ; five of the six are included 

 in the European twenty-three, and one of the five has been met with 

 in Australia. The British Devonian corals belong to twenty genera, 

 six families, and the three sub-orders, Zoantharia tabidata, Z. perforata, 

 and Z. rugosa. 



The genus Favosites, belonging to Z. tabulate, contains five species, 

 all of which have a wide geographical range. F. Goldfussii frequently 

 attains a very large size ; masses upwards of two feet in diameter are 

 sometimes met with. It is also remarkable for its great distribution 

 in space, occuring in Devonshire, at Nehou and Vise in France, at 

 at Millar in Spain, in the Oural, in the states of Ohio and Kentucky 

 in America, and in New South Wales ; yet it was confined to the 

 Devonian era. It was formerly confounded with F. Gotklandica, a 

 Silurian species. F. cervicornis is remarkable for its great abundance 

 in certain localities : at East Ogwell, near Newton, a very consider- 

 able mass of limestone seems to be entirely composed of it, to the 

 almost total exclusion of other fossils. F. fibrosa occurs also in 

 Lower Silurian rocks in South Wales, and in Upper Silurian in 

 Shropshire. 



Pleurodictyum problematicum is the only species, not only of the 

 genus, but also of the family (Poritidce), and even the sub-order 

 (Zoantharia perforata) which occurs in Palaeozoic rocks, all its affinities 

 are with organisms of much later times : it is a small islet of vitality, 

 separated by a vast ocean of time from the organic continent to which 

 it belongs. In Britain it occurs in the slate rocks at Meadfoot, near 

 Torquay ; at Ogwell, near Newton ; an4 in great abundance, and of 

 great size, at Looe in Cornwall; but has not been found anywhere in 

 limestone. 



The genus Gyathopliyllum, belonging to the palaeozoic sub-order 

 Z. rugosa, contains fourteen species, that is, two-sevenths of the 

 entire series. A small reed-like variety of 0. cozspitosum occurs in 

 such numbers at one locality known as the Land's End, near Tor- 

 quay, as to furnish a very faithful example of a coral-reef of the 

 Devonian period. G. Bucldandii is the only British Devonian coral 

 not found in South Devon. 



Ghonophyllum perfoliatum is recorded as occurring in Upper 

 Silurian rocks as well as in Devonian ; its great vertical range sug- 

 gests the belief that it possessed a hardy plastic constitution, seeing 

 it had lived through changes such as must have been introduced 

 during lapses of time great as those represented by the terms 

 " Silurian" and " Devonian ;" and from such a constitution it might 

 bo supposed to have had a wide geographical distribution; never- 

 theless, it seems to have been particularly limited in this latter 

 respect, thus contrasting strongly with Favosites Goldfussii, which, as 

 lias been stated, circumnavigated the globe during the Devonian age, 

 to which it was confined; whilst ChoiwphyUum perfoliate.])!, wlrbh 



