470 Rojjorts and Proceedings — 



sides of the Atlantic is very interesting. On both continents it 

 presents three phases, those of the Lower, Middle, and Upper Erian, 

 and there is a remarkable correspondence of these in countries so 

 wide apart as Scotland, Belgium, Canada, Brazil, and Australia. 

 Examples of this were given in the Rhizocarps, at this period very 

 important, in the Lycopods, the Equisetaceas, the Ferns, and the 

 Conifers. . The number of coniferous trees belonging to Dadoxylon 

 and allied genera, and the abundance of ferns, often arborescent, 

 were especial features of the Middle and Later Erian. 



The flora of the Erian age culminated and then diminished. In 

 like manner that of the succeeding Carboniferous period had a small 

 commencement quite distinct in its species from the Erian ; it 

 culminated in the rich vegetation of the true coal formation, which 

 was remarkably similar over the whole world, presenting, however, 

 some curious local differences and dividing lines which are begin- 

 ning to become more manifest as discovery proceeds. Li the Upper 

 Carboniferous the flora diminishes in richness, and the Permian age 

 is, so far as known, one of decadence rather than of new forms. 

 Great progress has recently been made by Williamson and others 

 in unravelling the affinities of the coal-formation plants, and we are 

 on the eve of great discoveries in this field. 



Throughout the Silurian, the conditions do not seem to have been 

 eminently favourable to plants, but the few forms known indicate 

 two types of Acrogens, and one leading to the Gymnosperms, and 

 there is no reason to doubt the existence of insular land richly 

 clothed at least with the few forms of vegetation known to have 

 existed. 



In the Erian and Carboniferous there seem to have been two 

 great waves of plant-life, proceeding over the continents from the 

 north, and separated by an interval of comparative sterility. But 

 no very material advance was made in them, so that the flora of the 

 whole Paleeozoic period presents a great unity and even monotony 

 of forms, and is very distinct from that of succeeding times. Still 

 the leading families of the Rhizocarpece, Equisetacece, Lycopodiace(B, 

 Filices, and Coniferce, established in Paleozoic times, still remain ; 

 and the changes which have occurred consist mainly in the degrada- 

 tion of the three first-named families, and in the introduction of new 

 types of Gymnosperms and PliEenogams. These changes, delayed 

 and scarcely perceptible in the Permian and early Mesozoic, seem 

 to have been greatly accelerated in the later Mesozoic. 



5. — The Geological Age of the Acadian Fauna. 

 By G. F. Matthew, A.M., F.E.C.S. 



TN this sketch an attempt is made, by comparison with the 

 Cambrian fauna of other countries, and especially of Wales, 

 to fix more exactly than has hitherto been done the positicm of the 

 assemblage of organisms found near the base of the Saint John 

 group. The Trilobites are taken as a criterion for this purpose. 

 A brief statement of the position and thickness of the beds is given, 

 showing the relation of the fauna to the formation as a whole. 



