OP CONCHOLOGY. 217 



Possibly conditions may have changed within a few years ; 

 but it seems to me more reasonable to surmise that localities 

 have not always been accurately stated by collectors, and the de- 

 scriptive naturalist has often located his species by conjectures 

 based upon their association in a package, rather than from posi- 

 tive statements, which correspondents sometimes forget to fur- 

 nish. 



I have endeavored, through Miss Law's assistance, to obtain 

 such information as would serve to render our knowledge of dis- 

 tribution reasonably accurate. But it may be presumptuous to 

 suppose that a perfect series of notes on the species of so large 

 a stream as the Holston might be the result of explorations 

 made in so short a time as two years. 



In the following notes I have been governed mostly by my 

 own convictions. In a few instances I have deferred to the 

 opinions of others whose more extended acquaintance with spe- 

 cies entitle their views to consideration. 



UNIONID^.— [Catalogue and Notes.] 



1. JJnio ^ so pus, Green. 



2. " alatus, Say. 



3. " areceformis, Lea. 



4. " Barnesianus ? Lea. Two specimens, hardly mature, 



are all that have been seen. Mr. Wheatley sug- 

 gested the species might be U. G-reenii, Con. That 

 species, however, belongs to a different system of 

 drainage (Alabama River). The shells under con- 

 sideration agreeing very nearly with Mr. Lea's de- 

 scription of U. Barnesianus, I have provisionally 

 adopted that name for them. 



5. " hiangulatus, Lea. 



6. " hrevidens, Lea. 



7. " ccelatus, Con. On the authority of Mr. Wheatley. 



8. " caperatiis, Lea. Regarded sometimes as a variety of 



U. dromas, Lea ; it seems to me to be a good spe- 

 cies. 



9. " capsceforniis, Lea. 



10. " circulus, Lea. 



11. " Clinchensis, Lea. My determination of this some- 



what common species may be questioned. 



12. " Oonradicus, Lea. Two young specimens, supposed to 



be Oonradicus, may prove to be subtentus, Say. 



13. " Cooperianus, Lea. 



14. " cornutus, Barnes. 



15. " crassidens, Lamarck. 



