886 PROCEEDINGS OP tBE NATIONAL .l/r.s'/.T.V. VOL.SXII. 



strongly arched, curved behind and incurved in front of the beaks; the 

 lower psetidocardinal in the right valve largest, often much split up 

 into denticles, pseudocardinals of the left valve variable, dentellate; 

 two lower anterior scars deep, united, the upper very deep, separate. 

 Animal unknown. 



Section CYCLOMYA Simpson, 1900. 



(Type, Unio funebr all* Lea.) 

 tDIPLODON GRATUS Lea. 



*Unio grains LKA, Pr. Ac. N. Sci. Phila., IV, 1860, p. 91; * Jl. Ac. N. Sci. Pbila., 

 V, 1863, p. 382, pi. XLIII, fig. 290; * Ob.s., X, 1863,pl. XLIII, fig. 290. SOWERBY, 

 Conch. Icon., XVI, 1868, pi. LXXXIV, fig. 444. *P.KTEL, Conch. Sain., Ill, 

 1890, p. 154. 



*Margaron ( Unio) yratus LEA, Syu., 1870, p. 56. 



Uruguay River, South America. 



tDIPLODON PATELLOIDES Lea. 



* Unio patelloides LEA, Pr. Ac. N. Sci. Phila., IV, 1860, p. 89; Ml. Ac. N. Sci. 



Phila,., V, 1863, p. 383, pi. XLIII, fig. 291; *Obs., X, 1863, p. 19, pi. XLIII, 

 fig. 291. 

 *Margaron ( 1'irio) patelloides LEA, Syii., 1870, p. 56. 



Amazon River. 



tDIPLODON PER^FORMIS Lea. 



*Unio perceformis LEA, Pr. Ac. N. Sci. Phila., IV, 1860, p. 90; Ml. Ac. N. Sci. 



Phila., V, 1863, p. 384, pi. XLIII, fig. 292; *Obs., X, 1863, p. 20, pi. XLIII. fig. 



292.* SOWERBY, Conch. Icon., XVI, 1868, pi. LXXXIV, fig. 443. *P.ETEL, 



Conch. Sam., Ill, 1890, p. 163. 

 "Maryaron ( Unio) perveformls LEA, Syn., 1870, p. 55. 



Uruguay Eiver, South America. 



tDIPLODON FONTAINIANUS d'Orbigny. 



* Unio fontainiana D'ORBIGNY, Guer. Mag., 1835, p. 36. 



* Unio fontainianus HANLEY, Biv. Shells, 1856, p. 384, pi. xxi, fig. 27. * SOWERBY, 



Conch. Icon., XVI, 1868, pl.LXXXvn, fig. 466. ' P.ETEL, Conch. Sam., Ill, 

 1890, p. 153. * vox IIIERING, Arch, fiir Nat., 1893, p. 90. 

 *Margaron ( Unio) fontainianus LEA, Syn., 1870, p. 56. 



* Unio foniaineana D'ORBIGXY, Voy. Am. Mer.,1843, p. 605, pi. LXIX, figs. 6, 7. 



* HOPE, Anim. Nouv., 1857, p. 82. 



Parana Eiver, southern Brazil. 



tDIPLODON ROTUNDUS Wagner. 



*Unio rotundus WAGNER,' Test. Fluv. Bras., 1827, p. 34, pi. xxv, figs. 3, 4. 

 *MORICAND, Mem. His. Soc. Gen., 1838, p. 49, pi. iv, figs. 12-14. " KUSTER, 

 Conch. Cab. Unio, 1856, p. 160, pi. XLVI, figs. 1, 2. * SOWKRBY, Conch. Icon., 

 XVI, 1868, pi. LXXII, fig. 369. P^TEL, Conch. Sam., Ill, 1890, p. 166. 



*Margaron ( Unio) rotundus LEA, Syn., 1870, p. 56. 



Brazil. 



1 Uiplodon rotundum Spix in explanation of plate. 



