260 [February, 



Unio vibex, Con. New Fresh Water Shells, 31, 4, 3. 

 icff, Synopsis, 30. 



Whiteanus, Lea^ 1852, x. 258, 14, 8, Synopsis 33. 



Zeiglerianus, "Lea, 1838 (Zieglerianus ?) vi. 32, 10, 27. Synopsis, 29. 

 Chenu, Conchyl. Unio, pi. 24, fig. 2. 



Metaptera, Raf., Agas. 



Metap. alata. 



U. alata. Say, Nicholson's Encyclopedia, iv. pi. 4, fig. 2. 



Lam. Anim. sans Vert. 1819, vi. 76. Desk. ed. of Lam. vi. 539. 



Symphynota alata, iea^, iii. 448. U. alatus. Synopsis, 19. 



Barnes, Sillim. Journ. vi. 260. 



Co7i.y Monog., 5Q, 31. 



Metaptera megaptera. Raf., Ann. v. 34, 80, 20, Poulson's Trans. 29. 



Symphynota alata, Lea, iii. 448. U. alatus, Synopsis, 19. 



Lymnadia alata. Swains. Malac. 265, 48. 



U. alatus, Kust. Chemn. Unio. 15, 1, 1. 



fragilis.* 



Elliptio fragilis, Raf. Ann. v. 29. Poulson's Trans. 22. 



U. fragilis. Swains., Zool. Illust. 1st ser. pi. 171. 



U. fragilis. Say, Amer. Conch. Syn. No. 6. 



Kust. Chemn. Unio, 19, 3, 1. 



U. gracilis, Barnes, Sillim. Journ. vi. 174. 



Symphynota gracilis. Lea, iii. 452. U. gracilis. Synopsis, 19. 



inflata. 



Symphynota inflata, Lea, iv. 99, 14, 28. 



U. inflatus, Oo?^. Monog. 57,32. 



Lea, Synopsis, in. 



Kust. Chem. Unio, 17, 2, 1. 



U. Alabamensis, Con., New Fresh Water Shells, p. 67. 



Ohiensis. 



Lastena Ohiensis, Kaf. Ann. v. 50, Poulson's Trans. 60. 

 U. laevissimus. Lea, iii. 444, 13, 23, Synopsis, 19. 



Plectomerus, Con. 



Shell subalated, obliquely plicated; cardinal teeth very thick, sulcated, the 

 posterior lobe directed towards the posterior extremity of the shell ; posterior 

 muscular impressions scarcely impressed, confluent. 



Plect. atromarginatus. 



U. atromarginatus, Lea, viii. 207, 13, 21, Synopsis, 19. 

 Chenu, Conchyl. Unio, pi. 28, fig. 6. 



Boykianus. 



U. Boykianus, Lea, viii. 208, 13, 22, Synopsis, 19. 

 Ghena, Conchyl. Unio, pi. 27, fig. 2. 



costal us. 



U. costatus, Raf. Ann. v. 49, Poulson's Trans. 57. 



Con. Monog. 17, 7. 

 U. undulatus, Barnes, Sillim. Journ. vi. 120, pi. 2. 

 Lea, Synopsis, 20. 

 U. latecostatus, Lea, 1845, x. 68, 1, 2. 



* I have not quoted Stimpson for this species, because he says that the Ohio 

 species is different from the shell usually regarded as the same, which inhabits 

 Lake Champlain, and he refers only to the latter. Rafinesque described the 

 Western shell. As Say's IT. alatus was found in Lake Erie, I do not know 

 whether Agassiz considers it the same as the Ohio river species, or as that of 

 Lake Champlain. 



