704 PROCEEDINGS OF THE NATIONAL .l/L r .S'AT M. 



* Unto (lihilattis SAY,' Am. Conch., VI, 1834. * CONRAD, New F. W. Shells, 1834, 



p. 68.* FERI-SSAC, Gner. Mag., 1835, p. 27. * CONRAD, Monog., V, 1836, ]>. 

 42, pi. xxi. "KrsTER, Conch. Cab.Tnio, 1852, p. 38, pi. vi, fig. 4.* CONRAD, 

 Pr.Ac. N. Sci. Phila,, VI, 1853, p. 248. 



* Unio tortilonns FERUSSAC, Oner. Mag., 1835, p. 28. 



* Unio arclatus FERI'SSAC, Guer. Mag., 1835. p. 29. 



*t Unio arctior LKA, Tr. Am. Phil. Soc , VI, 1838, p. 10, pi. iv, fig. 10; 2 Obs., II, 

 1838, p. 10, pi. iv, fig. 10. *TROSCHEL, Arch, fiir Naturg., V, 1839, Pt. 2, p. 

 234. *HANLEY, Test. JVIoll., 1842, p. 208; - Biv. Shells, 1843, p. 208, pi. xxn, 

 fig. 46." CATLOW and REEVE, Conch. Norn., 1845, p. 56. * CONRAD, Pr. Ac. 

 N. Sci. Phila., VI, 1853, p. 245.* KUSTER, Conch. Cab. Uiiio, 1861, p. 17!t, 

 pi. LVI, tig. 6.* H. and A. ADAMS, Gen. Kec. Moll., II, 1857, p. 491.* CIIKM , 

 111. Conch., 1858, pi. xxi, figs. 2, 2a, 2b.* f SOWFRBY, Conch. Icon., XVI, 1868, 

 pi. LXXXV, fig. 2. * B. H. WRIGHT, Check List, 1888. * P.KTEL, Couch. Sam., 

 Ill, 1890, p. 144. 



"Margarita (Unio) arctior LEA Syn., 1836, p. 39; 1838, p. 25. 



*Margaron ( Unio) arctior LEA, Syu., 1852, p. 38; 1870, p. 71. 



tUNIO GIBBOSUS var. ARCUS Conrad. 



* Unio areas CONRAD, Am. Jl. Sci., XXV, 1834, p. 340, pi. L, fig. 8 ; *NewF. W. Shells, 



1834, p. 67.* FERUSSAC, Guer. Mag., 1835, p. 29.* MOLLER, Syn. Nov. Gen., 

 1836, p. 1898. * HANLEY, Test. Moll., 1842, p. 207; *Biv. Shells, 1843, p. 207, 

 pi. xxni, fig. 46. * CATLOW and REEVE, Conch. Nom., 1845, p. 56. * CONRAD, 

 Pr. Ac. N. Sci. Phila., VI, 1853, p. 245." H. and A. ADAMS, Gen. Rec. Moll., II, 



1857, p. 491.* B. H. WRIGHT, Check List, 1888." P^TEL, Conch. Sani., Ill, 

 1890, p. 144. 



* Margarita ( Unio) areas LEA, Syn., 1836, p. 38; 1838, p. 25. 

 *Marya'ron ( Unio) arena LEA, Syu., 1852, p. 38; 1870, p. 61. 



tUNIO GIBBOSUS var. SUBGIBBOSUS Lea. 



Tnio aubgibboaua LEA, Pr. Ac. N. Sci. Phila., IX, 1857, p. 169; Jl. Ac. N. Sci- 

 Phila., IV, 1858, p. 53, pi. vi, fig. 36; Obs., VI, 1858, p. 53, pi. vi. fig. 36. 

 * B. H. WRIGHT, Check List, 1888. * SIMPSON, Pr. U. S. Nat. Mua., XV, 1892, 

 p. 432, pi. i.xxvin, fig. 5. 



*Marf/aron ( Unio) subyibbosHS LEA, Syn., 1870, p. 61. 



* Unio lazarus SOWKRBY, Conch. Icon., XVI, 1868, pi. LXVIII, fig. 348. 



* t Unio rufns LEA, Pr. Ac. N. Sci. Phila., IX, 1857, p. 171 ; Jl. Ac. N. Sci. Phila., IV, 



1858, p. 85, pi. xvn, fig. 65; Obs., VI, 1858, p. 85, pi. xvn, fig. 65.* B. H. 

 WRIGHT, Check List, 1888. 



*Margaron ( Unio) rufus LKA, Syn., 1870, p. 61. 



fUNIO GIBBOSUS var. ARMATHWAITENSIS B. H. Wright. 

 *Unio gibbosus var. armatlncaitens'w B. H. WRIGHT, Naut., XI, 1898, p. 123. :! 

 tUNIO GIBBOSUS var. DELICATUS Simpson.' 



Entire Mississippi drainage; St. Lawrence and its tributaries; Ala- 

 bama River system; southeast into Florida; southwest to the Guada- 

 lupe Elver, Texas. 



'As of Rafiuesqne. I am unable to make out Rafinesque's species. 



2 Merely a form with white nacre. 



3 These three are dwarf varieties of gibbosvs. All are often more or less humped, 

 and there are many intermediate and connecting specimens. 



4 A greatly compressed, thin variety, with an evenly elliptical outline and very 

 dark nacre may bear this name. 



