‘He NAUTILUS. 
Vou. XI. MARCH, 1898. No. 11. 
MOLLUSCA CONTEMPORANEOUS WITH THE MASTODON. 
BY BRYANT WALKER. 
In THE Navrixus for March, 1891, (Vol. VI, p. 1381) there is 
given a list of half a dozen species of fresh-water shells which were 
found associated with the remains of a mastodon discovered in 
Randolph County, Indiana. ‘Through the courtesy of Mr. W. Hilles 
Smith of Niles, Michigan, I have recently had an opportunity of 
examining a quantity of material taken from the muck beneath the 
remains of a mastodon found near that city. 
As the list of species is a considerable one it is of interest not only 
because of the circumstances, under which they were found, but also 
as a basis for comparison with similar finds from other localities. 
As has been stated by others in reference to the mollusca formed 
fossil in the loess there is here, in most instances, little, if any, varia- 
tion from the usual form of the species as they are found living at 
the present time. 
The Planorbis companulatus Say and bicarinatus Say are both 
larger than the average size of the species as usually found. Inthe 
latter species there is a decided tendency towards a whorl narrow in 
proportion to its height, with a strong carina on both sides, result- 
ing in a long narrow aperture in mature examples. 
One of the most abundant species in the collection was Valvata tri- 
carinata Say, which afforded some unusual forms. As is well known, 
this species is extremely variable in its sculpture, ranging though 
the bicarinate and unicarinate forms to that which is ecarinate. In 
this, however, all the specimens are strongly tricarinate and the 
variation is in the other direction and in the form of additional ear- 
inz. This, in one instance, appears as a fourth carina on the body 
whorl about half way between the superior and peripheral carinz 
in the normal shell. In another specimen, a fourth carina is sud- 
