876 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxii. 



tDIPLODON LOCELLUS Lea. 



* Unio locellus Lea, Pr. Ac. N. Sci. Phila., X, 1866, p. 34 ; * Jl. Ac. N. Sci. Phila., VI, 



1868, p. 264, pi. xxxiii, fip-. 79; * Obs., XII, 1869, p. 24 pi. xxxiii, fig. 79. 



* Margaron ( Unio) locellus Lea, Syn., 1870, p. 47. 



Argentina. 



tDIPLODON SUAVIDICUS Lea. 



* Unio suavidiciis Lea, Pr. Ac. N. Sci. Phila., VIII, 1856, p. 95; *Obs., VI, 1857, p. 29, 



pi. XXIX, fig. 24; * Jl. Ac. N. Sci. Phila., Ill, 1898, p. 309, pi. xxix, fig. 24. 



* Margaron ( Unio) suavidiciis Lea, Syn., 1870, p. 54. 



Amazon. 



tDIPLODON BROWNII Lea. 



* Unio Irownii Lea, Pr. Ac. N. Sci. Phila., VIII, 1856, p. 95 ; * Obs., VI, 1857, p. 27, 



pi. XXIX, fig. 22 ; * Jl. Ac. N. Sci. Phila., Ill, 1858, p. 307, pi. xxix, fig. 22. 



* Margaron ( Unio) l)rownii Lea, Syn., 1870, p. 61. 



South America 1 Dr. Lea reports it from Mocha, Asia (with a ques- 

 tion), which is certainly an error. 



t DIPLODON LEAI Simpson.' 



"" Margarita ( Unio) modestus Lea, Syn., 1836, p. 32; 1838, p. 22. 

 "" Margaron ( Unio) modestus Lea, Syn., 1852, p. 33; 1870, p. 54. 



* Unio modestus H. and A. Adams, Gen. Rec. Moll., II, 1857, p. 493. 



Brazil. 



tDIPLODON RHUACOICUS d'Orbigny. 



* Unio rhuacoica d'Orbigny, Guer. Mag., 1835, p. 35 ; * Voy. Am. Mer., 1843, p. 606, 



pi. LXix, figs. 4, 5. 



* Margaron ( Unio) rJiuacoicus Lea, Syn., 1870, p. 54. 



* Unio rhyacoicus voN Martens, Mai. Bl., XV, 1868, p. 195. 



"" Monocondylwa rhyacaeca PiETEL, Conch. Sam., Ill, 1890, p. 147. 



Uruguay. 



tDIPLODON CHARRUANUS d'Orbigny. 



* Unio charruana d'Orbigny, Guer. Mag., 1835, p. 35; Voy. Am. Mer., 1843, p. 606, 



pi. Lxxijfigs. 8-14. 



* Margarita ( Unio) charruanus Lea, Syn., 1838, p. 20. 



' Lea credits this to Ferussac in his Synopsis, but I do not think it has ever been 

 described by that author or anyone else. In 1856 Kuster properly described and 

 figured a species in the Conchylien Cabinet (Vol. Unio, p. 147, pi. xliii, fig. 2) under 

 the name of Unio modestus, which he credits to Charpentier's manuscript, a different 

 shell from that referred to by Lea and the Adams brothers. If the latter was never 

 described the name modestus can not be used for it, as it was first properly applied.to 

 another species. The shells in Lea's collection may be described as follows : Shell 

 small, subrhomboid, rather solid; beaks full with radial sculpture, the two middle 

 bars coalescing; surface faintly concentrically sculptured, dark olive; two com- 

 pressed pseudocardinals in each valve which are strongly obliquely striated ; two 

 laterals in the left valve and one in the right; anterior muscle scars distinct; 

 nacre bluish; beak cavities shallow. Length 28, height 17, diameter 13 mm. 



