48 Trans. Acad. Sci. of St. Louis. 



Keeve also figures, as this form, a shell on Plate XXIII, 

 Vol. XVI, figure 106, which is certainly some other species. 

 Correcting the error in the addendum to Unio he quotes Con- 

 rad, who thinks that the shell may be Unio kienerianus Lea. 

 It is certainly much like it. 



This is a rare species, and will probably always be so con- 

 sidered. It has not occurred to any collector outside of 

 Louisiana, though it has been found in other than the original 

 locality. There is a fine specimen in my collection which was 

 recently obtained in Crass Lake near Shrevesport, Louisiana, 

 by Mr. Wayland Vaughan, that is very characteristic indeed. 

 Besides, there is before us a suite of three specimens that form- 

 erly belonged to Dr. Gerard Troost, of Nashville, Tenn., a 

 warm personal friend of Thomas Say, and a member, for a 

 time, of the singular community which sprang up at New Har- 

 mony, Indiana. To him Say gave these examples of his glebu- 

 lus, the original label of which is still treasured with the 

 specimens. They came into my hands through the kind 

 liberality of Dr. J. Berrien Lindsley, of Nashville, who became 

 the owner of Troost's collection, or of most of it. The history 

 is complete, and there is no question that this lot has passed 

 nnder the inspection of the great naturalist who described it 

 as new. The suite is from the Bayou Teche, Louisiana. 



Lamarck described this shell in the following terms: — 



" C7. testa elUptico-rotundata , inferne ventricosa^ sub epi- 

 derme splendide margaritacea ; cardine arcuato. Hahite 

 * * * . Coquille rare^ d^une forme singuUere pour le 

 genre i et dont la nacre est argent ee^ legerement teinte de rose, 

 irisee et tres hrillante. Largeur, 78 millimetres. Elle a un 

 pli sur le cote anierieur.'" 



The "silvery nacre" indicated by Lamarck has been ex- 

 hibited by but one specimen which has come to our notice. 

 The original description of Unio suborbiculatus Lamarck comes 

 nearer to the conditions exhibited by this shell, but the example 

 must have been a verv large one. To connect the two better, 

 in the mind of the reader, it is only necessary to add that 

 Lamarck himself gives Say's glebulus as a synonym, that 

 is to say, this has been done by Deshayes, who edited the 

 second edition of the Animaux sans Vertebres. Lea, who 

 saw the original example of Unio rotundatus, in the collec- 



