Occasional Papers of the Museum of Zoology 65 



Genus Dysxomia Agassiz, 1852 

 Type: Unio foliatus Hild. = Obliquaria Hexuosa Raf. 



Truncilla Rafinesque, '20, p. 300 (no type named) ; Herrmannsen, 

 '47, p. 627 (type, Truncilla truncata Raf.) ; Agassiz, '52, p. 44 (no type 

 named, first species, Tr. triquetcr Raf.) ; Simpson, '00, p. 516 (type, 

 Tr. triqucter Raf.). 



Dysnoinia Agassiz, '52, p. 43 (no type named, first species, Obli- 

 quaria flextiosa Raf.) ; Simpson, '00, p. 521, as subgenus of Truncilla 

 (type, U. foliatus Hild. = 06/. flextiosa Raf.). 



Since the type of Tniu cilia has been designated by Herr- 

 mannsen as Ti'. truncata Raf., this name takes the place of 

 Aniygdalonaias (which see). The next available name for 

 this genus is Dysnoniia Agassiz, the type of which has been 

 fixed by Simpson. 



Subgenus Truncillopsis n. n. 



Type: Truncilla triqueter Raf. 



Truncilla (subgenus) Simpson, "oo, p. 517 (type, Truncilla triqucter 

 Raf.). 



The removal of Truncilla and the extension of the subgen- 

 eric name Dysnomia to cover the whole genus necessitates the 

 introduction of a new subgeneric name for what was hitherto 

 the subgenus Truncilla s. s. of Simpson. The name of Trtm- 

 cillopsis is therefore proposed. 



Dysnomia (Truncillopsis) triouetra (Rafinesque), 1820 

 Type locality: Falls of the Ohio (at Louisville, Ky.). 



Truncilla triqucter Rafinesque, "20, p. 300, pi. 81, f. 1-4. 



Unio triangularis Barnes, '23, p. 272, pi. 13, f. 17. 



Unio cuneatus Swainson, Phil. Mag., '23. p. 112. 



Unio formosus Lea, '31 (not '34, as given by Simpson), p. ill, pi. 

 16, f. 31- 



U. triquetcr Raf. = U. triangularis Bar. =r U. formosus Lea = U. 

 cuneatus Sw., Conrad, '34, p. 72; Ferussac, "35. p. 27. 



Truncilla triquetra Raf., Simpson. '14, p. 5. 



Truncilla triquetra Raf., Vanatta, '15, p. 550 ("type" examined). 



