In the Western Hemisphere, both in Canada and as far south as the 40th and even 38th parallel of latitude in the United States, we meet with a repetition of all the peculiarities which distinguish the European boulder formation. Fragments of rock have travelled for great distances from north to south; the surface of the subjacent rock is smoothed, striated, and fluted; unstratified mud or _till_ containing boulders is associated with strata of loam, sand, and clay, usually devoid of fossils. Where shells are present, they are of species still living in northern seas, and half of them identical with those already enumerated as belonging to European drift 10 degrees of latitude farther north. The fauna also of the glacial epoch in North America is less rich in species than that now inhabiting the adjacent sea, whether in the Gulf of St. Lawrence, or off the shores of Maine, or in the Bay of Massachusetts. At the southern extremity of its course, moreover, it presents an analogy with the drift of the south of Ireland, by blending with a more southern fauna, as for example at Brooklyn near New York, in lat. 41 deg. N., where, according to MM. Redfield and Desor, _Venus mercenaria_ and other southern species of shells begin to occur as fossils in the drift. The extension on the American continent of the range of erratics during the Pleistocene period to lower latitudes than they reached in Europe, agrees well with the present southward deflection of the isothermal lines, or rather the lines of equal winter temperature. Formerly, as now, a more extreme climate and a more abundant supply of floating ice prevailed on the western side of the Atlantic. Another resemblance between the distribution of the drift fossils in Europe and North America has yet to be pointed out. In Norway, Sweden, and Scotland, as in Canada and the United States, the marine shells are confined to very moderate elevations above the sea (between 100 and 700 feet), while the erratic blocks and the grooved and polished surfaces of rock extend to elevations of several thousand feet. [Illustration: Fig. 118. Cross section. K. Mr. Ryland's house. _h_. Clay and sand of higher grounds, with _Saxicava_, &c. _g_. Gravel with boulders. _f_. Mass of _Saxicava rugosa_, 12 feet thick. _e_. Sand and loam with _Mya truncata_, _Scalaria Groenlandica_, &c. _d_. Drift, with boulders of syenite, &c. _c_. Yellow sand. _b_. Laminated clay, 25 feet thick. A. Horizontal lower Silurian strata. B. Valley re-excavated.]