A great number of fossil Unios were collected by Barnum Brown from the Laramie clays, 130 miles northwest of Miles City, Montana. 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 palæontologists, 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 biæsopoides, Unio æsopoides and Unio æsopiformis, all resembling U. æsopus 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 palæontological 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 1000 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 in Lake Constance; nor was there any evidence of shells, broken or otherwise, observed by him in the excavations in the lake-dwellings.
The curator of the Rhodesia Museum, Bulawayo, South Africa, states that in Rhodesia, in the vicinity of Bulawayo, beads made out of the shell of the common Unio or fresh-water mussel (Unio verreauxi) have been observed in the graves, although pearls themselves have never been found with them in any burials.
ADDENDA
One of the authors used every endeavor in 1893 and 1894 to have a bill passed by Congress for the regulation of pearl-fishing in the United States. These efforts were frustrated by the influence of the local pearl fishers. An attempt has now been made to preserve the industry in Illinois, where the legislature has this spring passed a bill for its regulation.