Equus idahoensis. E. excelsus? Protohippus? Rhinoceros, probably Aphelops (Teleoceras) fossiger. Mastodon mirificus. Cervus, possibly new. Smaller and more slender than C. canadensis. Procamelus, size of P. major. Tragocerus? horn-core of antelope. Ischyrosmilus n. sp. Morotherium leptonyx. Castor, possibly n. sp. Olor, size of O. paloregonus. Graculus idahoensis. In this collection the presence of horses of the genus _Equus_, of _Cervus_, _Morotherium_, and _Castor_, is strongly suggestive of the Pleistocene. The type of _Mastodon mirificus_ was found in Pleistocene deposits of probably Aftonian age. Although rhinoceroses are supposed to have become extinct before the end of the Pliocene, this supposition may be an error. The list of Blanco vertebrates is a short one, and the absence of a genus from it is not decisive. One drawing of a seine in the sea-waters of Florida would furnish inadequate materials for conclusions about the fish fauna of that coast. The Thousand Creek fauna (Merriam, Bull. Dept. Geol. Univ. Calif., vol. X, p. 429), which to the present writer appears of about the same age as the Blanco, contains a species of _Teleoceras_. The genera _Protohippus_ and _Procamelus_ might be supposed to have continued their existence and evolution until interrupted by an age of ice and by competitors from Asia. In 1917 (Bull. cit., vol. X, pp. 255–266) Merriam and Buwalda published a short list of fossils which they had collected along the Columbia River in Washington State. A horse was found which was referred to _Equus_ or _Pliohippus_; also two camelids, one of which was thought to be near _Pliauchenia_. Merriam concluded that the evidence on the whole favored the Pleistocene. The list will fit into the Nebraskan without difficulty. In 1889 (Amer. Naturalist, vol. XXIII, p. 253), Professor E. D. Cope published a list of fossil mammals collected in the “Oregon desert,” apparently somewhere in the region of Silver Lake or Summer Lake. The list is as follows: Canis sp. indet. Elephas or Mastodon. Holomeniscus or Auchenia. Aphelops sp. indet. Hippotherium relictum. Equus sp. indet. Cope looked upon this collection as remarkable in that it showed the presence of true horses and camels associated with a rhinoceros. He concluded that the fossils belonged to his Idaho formation. Dr. W. D. Matthew thought that the collection was a mixture of fossils from two formations (Bull. Amer. Mus. Nat. Hist., vol. XVI, p. 321). It may, however, have been made in Nebraskan deposits. In 1921 (Proc. U. S. Nat. Mus., vol. LIX, pp. 617–638), the writer described a collection of vertebrate remains from Anita, Coconino County, Arizona. These remains were found in a cave in making explorations for copper ore. The list follows: