The
shells were found in a bed situated about 180 feet above the Fort
Pierre shales and, therefore, well above the recognized cretaceous
strata. These shells were in fairly good condition and retained the
nacreous coloring to a considerable extent. As some of them resemble
the modern species, it seems that the same designations might be
applied to them.
Prof.
R. P. Whitfield, one of our greatest palaeontologists, who has
carefully examined these fossil shells, suggests that they are
probably the progenitors of the species of Unios and fresh-water
mussels that now inhabit the Mississippi and Wisconsin rivers and their
tributaries, and he proposes the following names for some of them,
indicating at the same time the living species with which he compares
them: Unio biœsopoides, Unio œsopoides and Unio œsopiformis, all resembling U. cesopus Green ; Unio letsoni = U. cornutus Barnes ; Unio cylindricoides = U. cylindricus Say ; Unio gibbosoides = U. gibbosus Barnes ; Unio pyramidatoides = U. pyramidatus Lea ; Unio retusoides -U. retusus Lam. ; Unio verucosiformis = U. verrucosus Barnes.
Although
it is almost certain that these ancient Unios were pearl-bearing,
Professor Whitfield informs us that, in a period of fifty years of
palseontological research, he has never found a fossil pearl.
We
are informed by Sophus Müller, Director of the Royal Danish Museum of
Antiquities at Copenhagen, that no Danish ornaments containing pearls
have been found dating from an earlier period than iooo b.c. ; he also states that no fresh-water pearls have ever been discovered in the Danish graves.
Dr.
H. Ulmann, director of the great Swiss Landesmuseum at Zurich, and Dr.
Otto Leiner, director of the Rosengarten Museum at Constance,
personally communicated to us that no pearls exist in either of the
collections of these great museums, nor to their knowledge have any
been discovered in the lake-dwellings or the prehistoric graves of
either Switzerland or Baden. This may either be due to conditions
favorable to the dissolution of the pearl by the action of the ooze on
the lake bottom, or else to the entire absence of knowledge of them on
the part of a people who were familiar with many materials, since the
museum collections even show jade implements of a number of types.
Dr.
Leiner, whose father was curator of the Rosengarten Museum before him,
informs us that at Bodman on Lake Constance there were found a large
number of bored cylinders, from one fourth of an inch to one inch in
length, made out of limestone. They were used for necklaces, somewhat
in the style of our Indian wampum, and were either worn alone or in
connection with bored cylinders made of the tuff-rock and also of
encrinite stems.
Dr. Leiner also asserts that he has never seen Unio margaritifera
