THE LOESS AND THE LANSING MAN. 33 1 



reports on fossils is to be found in misconception of species 

 and incorrect identification. For example, what was gener- 

 ally reported as Vallonia pulchella from the loess is J r allohia 

 gracilicosta, a northwesterly upland species; under fossil 

 Succiuea obliqua were included two, possibly three species; 

 Carychium exiguum (reported as semi-aquatic by Call, in 

 paper on Des Moines loess, 1. c, p. 16!) has not been found in 

 the loess, the fossil species being C. exile, a decidedly upland 

 species ; the form commonly reported by earlier writers as 

 Pupa blandi is Difidariq pentodon (though P. bland/ occurs in 

 the loess), and possibly a Vertigo; and other instances might 

 be cited showing that species were not clearly recognized by 

 conchologists, and in consequence comparisons of fossil shells 

 were sometimes made with recent shells of different species. 

 Manifestly conclusions drawn from such comparisons are val- 

 ueless. 



Both Drs. Chamberlin and Salisbury, and Professor McGee, 

 relied upon such information and were misled by it. The 

 aquatic shells of the loess are relatively very few, and all of 

 that type which inhabit small ponds. There is not a single 

 well authenticated species of fluviatile molluscs known from 

 clearly undisturbed loess in this country! And yet reference 

 is constantly made to the few paltry pond snails, coupled with 

 vague references to "semi-aquatic" forms, while the vastly 

 greater number of truly terrestrial and upland species is made 

 subordinate! 



The writer thus refers to these details at some length to 

 show that the supposed information upon which these emi- 

 nent authors based their conclusions, at least in large part, 

 was erroneous, and that consequently the conclusions them- 

 selves cannot be entirely correct. Mere reference to these 

 conclusions, therefore, does not settle the case. Both the 

 great works cited represent the results of pioneer efforts, and 

 were not primarily concerned with the origin of loess, that 

 question being largely incidental. With this prop removed 

 there remains nothing but generalities for the support of the 

 recent revival of the glacio-fluviatile theory. 



