40 IOWA ACADEMY OF SCIENCES. 



region, and their presence is no proof of a glacial climate, but 

 may suggest a drier climate.* 



3. Mammals. — The evidence furnished by the mammals is 

 unsatisfactory, since in some cases, at least, there is doubt that 

 the remains came from unmodified loess. Several species 

 have been reported! all of them herbivorous and rare. 



The scarcity of material, however, does not necessarily show 

 that these forms were very rare (thus suggesting limited land 

 areas), for we have quite the same difficulty in finding the 

 bones of more modern mammals. The bones of the bison, deer, 

 bear, etc., are seldom found, yet the species were once common. 

 The rabbit and squirrel leave but few traces of their existence, 

 yet they are common even now. 



The presence of the fossil mammals, so far as it has any 

 value in the present discussion, indicates plenty of plant-food, 

 a possibility of extensive land areas over which these forms 

 roamed. 



Certain other questions, bearing largely on physical geogra- 

 phy, are suggested to the student of the fauna of the loess. 

 The fact that that the loess caps the hills haslong been known. 

 If the material was deposited in water, there must have been a 

 body of the latter sufficiently large to cover these hills, for it 

 is recognized that the general topography of this region was 

 determined before the loess was deposited. X If there was such 

 a large body of water, where are the evidences of its shore 

 lines'? It has been suggested§ that the waters were contained 

 within walls of ice, but that hypothesis calls for climatic condi- 

 tions which would make impossible the develoiDment of the life 

 of which we find evidences. 



Where, too, were the land areas upon which the molluscs 

 and mammals flourished? It might seem plausible at first 



* This was suggested by the author In Bull. Lab. Nat. Hist , State Univ. of Iowa, 

 Vol. ir, p. 94, but was not suflBciently emphasized. 



+The following have come to the author's attention: 



Bootherium eavifrons Leidy. G. Hambach. Bull. I, Geol. Sur. Missouri, p. 82. 



Castor fiber Ow. G. 0. Swallow, Geol. Sur. Mo., Vols I and II, p. 215; Hambach, 1. c, 

 p. 82. 



Cervus muscatinensis Lldy, F. M. Witter, Notes on the Loess; Rep. U. S. Geol. Sur., 

 Vol. XI, p. 471. 



Elephas primigenms Blume. Swallow, i.e. p. 215; W. H. Pratt, Proc. Dav. Acad. Scl., 

 Vol. I, p. 98; Hambach, 1. c. p. 82; W. J. McGee, Rep. U S. Geol. Sur., Vol. XI, p 471 

 (quoted from Pratt, 1. c). 



Mastodon giganteus Cur., Swallow, 1. c, p. 215: Hambach, 1. c. p. 82. 



$To this Prof. S. Oalvin again recently calls attention in Geol. Sur. Iowa, Vol. V 

 p. 69. 



§McGee and Call,— On the Loess and Associated Deposits of Des Moines, pp. 22-3; 

 McGee,— Rep. U. S. Geol. Sur., Vol. XI, p. 574. 



