146 Trans. Acad. Sci. of St. Louis. 



EXPLANATION OF ILLUSTRATIONS. 



Plate XI. 



1, Lampsilis alata Say; la^ right valve of same, showing fold. — 2, Unio 

 gibbosus Barnes. — 3, Lampsilis ligamentina Lamarck. — i, Unio gibbosus 

 Barnes. — 5, Lampsilis ligamentina Lamarck. 



Issued November 26, 1901. 



