WILLIAMS.] J. w. DAWSON. 237 



anomaly to have a stratum of rocks include one flora and a part of 

 another almost entirely distiuct and characteristic of another period. 

 But he thinks the gap greater in Eastern America between the Devo- 

 nian and Carboniferous periods than it is elsewhere. The Ohio plants 

 mentioned indicate passage beds, but in that case the author would 

 suppose them to be newer than the Chemung group, and wanting or 

 represented by barren deposits in New York. 



In another paper, 1 which is copied into the American Journal of 

 Science, from the Quarterly Journal of the Geological Society (with the 

 exception of Part n, containing desciiptions of species, which is omitted), 

 Dr. Dawson speaks of the large number of species of the Devonian flora, 

 more than 60, which he has had the opportunity of examiniug, from the 

 collections of Messrs. Matthew and Hartt, Professor Hall, and Professor 

 Hitchcock, and notices the geological character of the localities in which 

 they are found, with lists of the fossils found in each. The localities 

 are in the States of New York and Maine, in Canada and New Bruns- 

 wick. The rocks of St. John in New Brunswick, from which a copious 

 flora has been obtained, are described in detail, and a summary given 

 of the deposits. 



At the close conclusions are drawn from the observations recorded in 

 the preceding part of the article as follows : (1) Tbat the Devonian 

 flora resembles the Carboniferous in its general character in the pre- 

 valence of Gymnosperms and Cryptogams, and the generic types of the 

 two periods are nearly the same. Of thirty-two genera described, only 

 six are peculiar to the Devonian period, though some are much better 

 represented in the Devonian than in the Carboniferous, and -several 

 Carboniferous genera are wanting in the Devonian. (2) A majority of 

 the species of the Devonian do not reappear in the Carboniferous, but 

 a few species extend from the Upper Devonian into the Carboniferous, 

 establishing a passage from the earlier to the later flora. But this 

 connection is less close than that between the Lower Carboniferous and 

 the true Coal Measures. (3) A large part of the difference between 

 the two floras is owing to the different geographical conditions. (4) 

 The conditions were less favorable to the preservation of plants in the 

 Devonian than in the Carboniferous period. (5) The Devonian flora 

 was not of lower grade than that of the coal period, but we find in it 

 more points of resemblance to the floras of the Mesozoic period and of 

 modern tropical and austral islands than in that of the true coal forma- 

 tion. (6) The fades of the Devonian flora in America is very similar 

 to that of the same period in Europe, but the number of identical spe- 

 cies in the coal fields of the two continents is greater. These conclu- 

 sions do not differ materially from those of Goeppert, Unger, and Bronn, 

 after consideration of the Devonian flora of Europe. 



In a letter from Leo Lesquereux 2 the following points regarding cor- 



1 Dawson, J. W. : On the Flora of the Devonian period in Northeastern America. Am. Jour. Sci., 

 vols. 35, 36, 1863, pp. 311-319, 41, 42. 



2 Lesquereux, Leo : On the character of the Millstone grit or Suhcarhoniferous conglomerate in the 

 far West. Am. Phil. Soc, Proa, vol. 9, 1863, pp. 198-204. 



