30 Trans. Acad. Sci. of St. Louis. 



Selma, and the Eed river, at Shrevesport, very great develop- 

 ment. From all these localities we have seen large examples, 

 some of which are believed to be unrivaled elsewhere. 



Though Say's name of hews has strict priority, it cannot be 

 used for the followiug reasons : it was poorly described in 

 the beginning ; it was abandoned by its author for the name of 

 undulatxLs which had been given to another and distinct species 

 by Barnes, from which procedure it is clear that Say had no 

 clearly defined view concerning this form. Lea's name and 

 description being the first that was accompanied with figures, 

 and being the first clearly to indicate the limits of the species, 

 must be adopted, and his name is now in common use. Say 

 himself said, in his description of Plate XVI, American Con- 

 chology : «' I formerly considered this species, with much doubt, 

 as distinct from the iradulatus of Barnes, and gave to it the 

 name of heros, but notwithstanding some differences, I have 

 concluded, after a more mature examination and comparison, 

 that it may be with propriety referred to that species. Barnes 

 drew his description and figure from a specimen then unique, 

 * * * which was so eroded as not to exhibit the orna- 

 mental tubercles of the umbo and beak." To all who have 

 seen the perfect forms of undidatus Barnes and inidtiplicatus 

 Lea the marked diflferences in the characters of the beaks will 

 be clear. Say abandoned his name for this form, and another 

 student renamed it. 



This shell has occurred to us only in the St. Francis river, 

 so far as collections have been made in Arkansas. 



I have not seen a specimen of Unio gigas Svvainson, but a 

 specimen in the Museum Taylor, England, is figured by Reeve 

 as coming from the Ohio river. Vide Unio Plate LVI, Fig. 

 287, Conchologia Iconica, Vol. XVI, 18(^7. There can be no 

 question that this is also Unio midtipUcaiiis Lea, and that it 

 should be placed under the above synonymy. 



Reeve describes and figures a shell under the name of Unio 

 perpJicatns Conrad, in Conchologia Iconica, Vol. XVI, 

 Uiiio Plate IX, Fig. 35, which had been labeled by J. G. 

 Anthony, but which is most certainly a specimen of Unio 

 midtiplicatus Lea. The specimen was then in the Museum 

 Cuming. 



