DES MOfNES ACADEMY OF SCIENCE. 



*rnio trape/oides, Eea. 



(Trsms. Am. Phil. Soe., Vol. ]V, PI. Ill, Fig-. 1.) 



Alabama and Coosa rivers, Alabama: lower Mississippi river to Trinity rive'-. 

 Texas, r. xlixithuuix. of tlie Chattahooehee river, Georgia, is very close to this 

 form. 



*Unio triaiiinilaris, Barnes. 



(Am. .Jour, of Soi. and Arts, 1st Series, Vol. VI, PI. XIII, Figs. 17a, 17b.) 

 \Vestern New York to Michigan and Iowa; south to Tennessee river, in north 



* Unio trigomis. Lea. 



(Trans. Am. Phil. Soc., Vol. IV, PI. XVI, Fig. 40.) 



Tiiis species ranges from western New York to Minnesota and Iowa. It is a 

 member of the group typified by 77. rnb'ujinosus,, which see. Very turgid spec- 

 imens of the latter have been occasionally received as trigonus. 



t Unio troostii 9 Lea. 



(Tram. ATI. Phil. Soc., Vol V, PI. X, Fig-. 30, as 77. troostensis.) 

 Rock Castle river. Kentucky, and Cumberland, Clinch and Powell's rivers, 

 Tennessee. 



* Unio tuberoulatus, Barnes, 



(Am. Jour, of Sci and Arts, 1st Series. Vol. VI, PI. VII, Figs., 8a, 8b. Also finely 

 fis'urerl in Poulsen's translation of Ratinesquv's "liivulvo Shells of 

 th<> river Ohif)," in frontispiece, as U. verrucosa.) 



Ohio to Eto wall rivers, Georgia; Coosa, Alabama, Cahawba and Black War- 

 rior rivers. Alabama; to Minnesota and Kansas; south to Trinity river, Texas. 

 Notwithstanding the wide distribution of this well-known species it presents lit- 

 tle variation. The specimens from the Alabama streams are largely character- 

 ized by a purple nacre while the more northern forms are usually white. 



t Unh> tubd'osus, Lea. 



(Trans. Am. Phil. Soc. 2ml Scries, Vol. VIII, PI. XIV, Fi. ;!:>.> 



Caney Fork and Cumberland rivers, Tennessee, and Tennessee river, north 

 Alabama. Groups with U. ynetanevTUS, Ratinesque. 



t ATALOGUK 4*>. 



