GEOLOGY AND PALEONTOLOGY 7 



tion. Volume in goes into greater detail, comparing the 

 condition of glaciers in 1899 with their condition as pre- 

 viously observed, so as to infer changes, and making sys- 

 tematic records of the positions of ice fronts, in order to 

 facilitate future comparisons. It treats also of features 

 tending to throw light on problems of Pleistocene glacia- 

 tion in the eastern United States, discusses the Pleisto- 

 cene glaciation of Alaska, and incidentally makes a con- 

 tribution to earlier geologic history by describing certain 

 peneplains belonging to the pre-Pleistocene topography. 



A noteworthy result in stratigraphic geology is the cor- 

 relation, on fossil evidence, of slates and shales in three 

 widely separated localities Yakutat Bay, Prince William 

 Sound, and Kadiak Island and the determination of their 

 age as early Jurassic. The formation or series thus con- 

 stituted named Yakutat by Russell covers large areas, 

 is elaborately and intricately folded, and is the domin- 

 ant constituent of mountain masses which have a long 

 history, including base-leveling and subsequent uplift and 

 dissection. 



The Alaska Peninsula, which so bristles with volcanic 

 peaks as to appear from a distance characteristically 

 igneous, was found, at a point where narrowed by oppos- 

 ing bays, to contain a ridge of uplifted marine strata of 

 Eocene age. These strata contain a molluscan fauna, the 

 first of that age discovered in Alaska, and show also, 

 by their physical constitution, that the region was already 

 the scene of volcanic activity in early Tertiary time. A 

 collection of Eocene plants was also obtained from another 

 point on the coast of the peninsula. 



The paleontologic collections include a number of new 

 species, thirty-eight of which are described in this volume. 

 Twelve are Jurassic and the remainder Eocene. Of the 

 Jurassic species seven were found to be so peculiar as to 

 require the erection of new genera. 



