38 O NATURAL HISTORY BULLETIN. 



It will be seen that a large part of these species do not oc- 

 cur in the loess, or are exceedingly rare, and that 12 are aqua- 

 tic, — a much larger percentage than can be found anywhere 

 in true loess, notwithstanding the fact that the Missouri river 

 is poorer in aquatic forms than any other river within the 

 loess -covered territory. There is also a striking absence or 

 scarcity of such characteristic loess forms as Succinea gros- 

 venorii, S. avara, Pyramidula sttiatella, etc. The list in- 

 cludes only forms which were found in the "wreck-heaps," 

 and does not include other aquatic forms which are sometimes 

 found in somewhat different situations along the river. In 

 such cases as this the upland shells were carried down for 

 short distances, and their distribution is wholly unlike that of 

 the loess fossils, for they are more or less banded and heaped 

 together, a condition which is very rare in the loess, and en- 

 tirely local. 



But the most peculiar objection to the value of fossils is 

 made by Miss Owen on p. 227, 1. It is so absurd that but 

 for the fact that it was published in a scientific journal, and 

 hence might be credited by others who are unfamiliar with 

 the subject, it would go unnoticed. In order that comments 

 may be properly appreciated its most interesting parts are here 

 reproduced in full: " Professor Shimek asserts with much 

 positiveness that 'there is not a single well authenticated 

 species of fluviatile mollusks known from" clearly undisturbed 

 loess in this country.' Such a statement leaves no doubt as 

 to personal conviction, but carries no proof of its correctness, 

 so it may be asked if the loess fossils can be positively identi- 

 fied. On the subject of identification of snails Theodore Gill, 

 supporting his conclusions by those of Professor Huxley, says: 

 ' The same kind of shell may be common to forms that are 

 radically different in their organization, and there is no a 

 priori reason why the modifications of the shell should be of 

 any greater value than those of any other single part of the 

 organism .... It is thus seen that the form of the shell, and 

 even the presence or absence of a shell, are of very inferior 



