Geology. 321 



known paleontologist of the Carnegie Institution of Washington 

 constitutes almost the entire volume. In it Doctor Hay treats 

 exhaustively not only all Pleistocene mammals which have been 

 found within the limits of Iowa, but those which from their 

 known distribution may be expected to be found. He also discusses 

 in detail the skeletons and measurements of certain existing types to 

 enable the future discoverer of Iowa fossils more readily to identify 

 his material. Doctor Hay has already done valuable service in 

 his recognition of the various Pleistocene faunas, of which little 

 was clearly known before he began his studies, and the pres- 

 ent work furthers our knowledge of Quaternary animals very 

 materially. 



The Iowa Pleistocene contains a very large fauna, as its central 

 position and abundance of fossil-bearing localities would lead one 

 to expect, and this is discussed in much detail. Preliminary to 

 such description, however, the following topics are treated : Defi- 

 nition of the Pleistocene, division of the Pleistocene into its five 

 glacial and five interglacial periods, and a study of these times in 

 detail. The author next describes the loess, which covers practi- 

 cally the whole state except that part which is overlain by the 

 Des Moines lobe of the Wisconsin drift and some counties along 

 the southern border. Loess rarely overlies the Wisconsin drift. 

 Another section describes the localities in Iowa where Pleistocene 

 vertebrates have been found, and this subject is further elucidated 

 by a map. A bibliography follows. 



The second part of the work is entitled " The mammals of the 

 Pleistocene," and herein the paleontological discussion is found. 

 To enumerate the former briefly, there have been discovered : 



Of the ground sloths, two, Mylodon and Megalonyx ; five 

 horses, four of the genus Equus and one three-toed Neohipparion 

 doubtfully reported from the Aftonian ; no tapirs or rhinoceroses, 

 as the latter had become extinct, and the range of the former was 

 farther south. The artiodactyles are represented by at least three 

 pig-like animals related to the modern peccary, one camel, and 

 several deer, representing at least five genera, Odocoileus, Cer- 

 vits, Cervalces, Alces and Rangifer. In addition, there were the 

 prongbuck, a new goat, musk oxen, and bison, including at least 

 four and probably six species, two of which are as yet undiscov- 

 ered within the limits of the state. 



Proboscidea were an abundant and conspicuous element in the 

 Iowa Pleistocene, including two genera of mastodons, Mammut 

 and Rhabdobunus, the latter being a new name to take the place 

 of Dibelodon, which may prove a synonym. Of Mammut, Hay 

 recognizes two species : the common mastodon, M. americanum, 

 and a new form with large persistent lower incisors which he 

 calls M. progenium. The true elephants are represented by all 

 three American species, Elephas primigenius, E. columbi, and the 

 majestic E. imperator. 



Rodents must have swarmed over the state, but the only ones 

 which seem to be actually recorded from the Pleistocene are the 



