In Ireland the "drift" exhibits the same general characters and fossil remains as in Scotland and England; but in the southern part of that island, Prof. E. Forbes and Capt. James found in it some shells which show that the glacial sea communicated with one inhabited by a more southern fauna. Among other species in the south, they mention at Wexford and elsewhere the occurrence of _Nucula Cobboldiae_ (see fig. 120. p. 149.) and _Turritella incrassata_ (a crag fossil); also a southern form of _Fusus_, and a _Mitra_ allied to a Spanish species.[131-A] FOOTNOTES: [122-A] Chap. xvi. and the references there given. [122-B] Voyage in 1822, p. 233. [123-A] T. L. Hayes, Boston Journ. Nat. Hist. 1844. [124-A] See paper by the author, Phil. Trans. 1835, p. 15. [125-A] See above, section, p. 48. [125-B] Geol. of Fife, &c. p. 220. [129-A] For a full account of the drift of East Norfolk, see a paper by the author, Phil. Mag. No. 104. May, 1840. [130-A] Quart. Journ. Geol. Soc. vol. vii. p. 22. [131-A] Forbes, Memoirs of Geol. Survey of Great Britain, vol. i. p. 377. CHAPTER XII. BOULDER FORMATION--_continued_. Difficulty of interpreting the phenomena of drift before the glacial hypothesis was adopted--Effects of intense cold in augmenting the quantity of alluvium--Analogy of erratics and scored rocks in North America and Europe--Bayfield on shells in drift of Canada--Great subsidence and re-elevation of land from the sea, required to account for glacial appearances--Why organic remains so rare in northern drift--Mastodon giganteus in United States--Many shells and some quadrupeds survived the glacial cold--Alps an independent centre of dispersion of erratics--Alpine blocks on the Jura--Whether transported by glaciers or floating ice--Recent transportation of erratics from the Andes to Chiloe--Meteorite in Asiatic drift. It will appear from what was said in the last chapter of the marine shells characterizing the boulder formation, that nine-tenths or more of them belong to species still living. The superficial position of "the drift" is in perfect accordance with its imbedded organic remains, leading us to refer its origin to a modern period. If, then, we encounter so much difficulty in the interpretation of monuments relating to times so near our own--if in spite of their recent date they are involved in so much obscurity--the student may ask, not without reasonable alarm, how we can hope to decipher the records of remote ages.