Pliocene and Pleistocene. - Shattuck, George Burbank, b. 1869; Clark, William Bullock, 1860-1917; Hollick, Charles Arthur, 1857-1933; Lucas, Frederic Augustus, 1852-1929; Hay, Oliver Perry, 1846-1930; Sellards, Elias Howards, 1875-; Ulrich, Edward Oscar, 1857-1944 (Johns Hopkins press, 1906)