THE NAUTILUS. 



VOL. XVIII. JANUARY, 19O5. No. 9. 



ON AN INTERESTING FOSSIL UNIO FROM WISCONSIN. 



BY GEORGE WAGNER. 



A little over a year ago Mrs. George Marston, of Quincy, Illinois, 

 presented to the University of Wisconsin the mollusca brought to- 

 gether by her late husband, an arderxt and an able collector of our 

 Wisconsin forms. The collection was placed in my hands for ar- 

 rangement. In looking it over I was immediately attracted by a 

 single somewhat broken valve of a Unio, evidently fossilized, and 

 the only fossil form in the collection. 



Mrs. Marston had very kindly, and very wisely, sent with the col- 

 lection all of her husband's correspondence relating to it. In look- 

 ing over the letters I came across a copy of one written by Mr. 

 Marston, and containing the necessary locality data for this shell. 



According to this letter the .>hell was found about 1889 in the 

 city of Green Bay, Wisconsin, during excavations for the city water- 

 works reservoir. It came from a depth of about fifteen feet below 

 the surface, and presumably from the till. 



i: As Mr. Marston well knew, the shell is wholly unlike any Unionid 

 now found in Wisconsin. It is a left valve, quite heavy but very 

 brittle. When found, the outer surface still retained most of the 

 epidermis, but this has almost entirely disappeared. The height is 

 70 mm., the breadth of the single valve approximately 22 mm. 



The shell when complete was very evidently smooth, with a rather 

 elliptical .outline. The' wall is thick but thins down cmisidiM-aMy 



