660 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxii. 



Conch. Cab. Ano., 187.5, p. 210, pi. lxiv, figs. 4, 5.— ^B. H. WiiiGHr, Check 

 List, 1888.— *P^TEL, Couch. Sani., Ill, 1890, p. 178. 



*Mar(jaron (Anodonta) denigrata Lea, Syn., 1852, p. 50; 1870, p. 79. 



*fAnodonta oblita Lea, Tr. Am. Phil. Soc, X, 1-52, p. 290, pi. xxviii, fig. 52; 

 * Obs., V, 1852, p. 46, pi. xxviii, fig. 52.—* Conrad, Pr. Ac. Nat. Sci. Phila., VI, 

 1853, p. 264.— *H. and A. Adams, Gen. Eec. Moll., II, 1857, p. 502,— *Clessin, 

 Conch. Cab. Ano., 1875, p. 165, pi. Liv, figs. 7, 8.—* B. H. Wkigiit, Check List, 



■*Margaron (Anodonta) ohlita Lea, Syn., 1852, p. 50; 1870, p. 79. 



'''Anodon suioylindmcea Sowerby, Conch. Icon., XVII, 1867, pi. xiv, fig. 47. 



"Anodonta suicylindracea Clessin, Conch. Cab. Ano., 1873, p. 92, pi. xxvi, figs. 6, 7. 



tANODONTOIDES FERUSSACIANUS var. SUBCYLINDRACEUS Lea. 



* \ Anodonta subcylindracea LEA,Tr. Am. Phil. Soc, VI, 1838, p. 106, pi. xxiv, fig. 117 ; 



*Obs.,II, 1838,p. 106,pl.xxiv, fig. 117.— *Troschel, Arch, fiir Nat., V, 1839, 

 Pt. 2, p. 239.—* Han.ley, Test. Moll., 1842, p. 223; * Biv. Shells, 1843, p. 223.— 



* Stimpson, Shells of N.Eiig.,1851,p. 15.— *Conrad, Pr. Ac. Nat. Sci. Phila., 

 VI, 1853, p. 264.—* H. and A. Adams, Gen. Rec. Moll., II, 1857, p. .503.— * Latch- 

 ford, Tr. Ottawa F. N. Club, 1882,p. 55.—* B. H. Wright, Check List, 1888.— 

 *PiETEL, Couch. Sam., Ill, 1890, p. 185.— * Walton, Moll. Monroe Co., 1892, 

 p. 17, pi. VIII, fig. 3. 



* Margarita (Anodonta) suhct/Kndracea Lea, Syn., 1838, p. 32. 



''Anodon subcylindracea De Kay, Zool. of N. Y., Pt. 5, 1843, p. 200, pi. xvi, fig. 229.— 



* Catlow and Reeve, Conch. Norn., 1845, p. 68. 



*Margaron (Anodonta) sulcylindracea Lea, Syn., 1852, p. 51; 1870, p. 82. 

 " Anodontoides siihcylindraceus Baker, Moll. Chicago, Pt. 1, 1898, p. 74, pi. iv, fig. 

 4; VI, fig. 1. 



ANODONTOIDES FERUSSACIANUS var. MODESTUS Lea. 



* \Anodonta modesta Lea, Pr. Ac. Nat. Sci. Phila., 1857, p. 84; *J1. Ac, Nat. Sci. 



Phila., IV, 1860, p. 364, pi. lxhi, fig. 189; *0b8., VIII, 1860, p. 46, pi. lxiii, fig. 



189.— * Clessin, Conch. Cab. Ano., 1874, p. 153, pi. xlix, figs. 7, 8.— *B. H. 



Wright, Check List, 1888.— *P.£TEL, Couch. Sam., Ill, 1890, p. 182. 

 "Margaron (Anodonta) modesta Lea, Syn., 1879, p. 79. 

 "Anodon modestns Sowerby, Couch. Icon., XVII, 1867, pi. x, fig. 26. 



Mississippi drainage area generally; St.LawrenceEiver system; Ked 

 Eiver of the IsTorth; Saskatchewan liiver; Connecticut.? The varieties 

 are found in the St. Lawrence system. 



Genus PEGIAS Simpson, 1900. 

 (Type, Margaritana fabula Lea.) 



Shell small, thickened in front, with a sharp posterior ridge, in front 

 of which is a wide radial depression, ending in a basal sinus; above 

 this ridge is another, making the shell decidedly biangulate and trun- 

 cate behind; beak sculpture consisting of subconcentric corrugations, 

 generally swollen on the posterior ridge; epidermis decorticated, but 

 showing a few dark, radial rays on the base of the shell ; pseudocardi- 

 nals rather solid; laterals wanting. Animal having the marsupium 

 empty in the specimen examined; inner gills larger in front, free from 

 the abdominal sac, all four truncated behind; palpi large; mantle with 

 square spots on its edge; branchial opening with a few large papillte; 

 anal opening smooth, not separated from the superanal. 



