NO. 1205. SYNOPSIS OF THE NAIADES— SIMPSON. 873 



branchiae rather large, angular at base, inner much the larger, united 

 their whole length to the abdominal sac; palpi scarcely projecting 

 posteriorly; mantle very thin, thickened on the edges; branchial open- 

 ing papillose, separated from the smooth anal opening by a strong 

 bridge; superanal opening not closed below. 



Subgenus DIPLODON Spix, 1827. 



Beak sculpture consisting of unbroken ridges, covering the whole 

 beaks. 



Animal having the labial palpi rounded below and at posterior base, 

 scarcely projecting behind. 



(Type, Diplodon ellipticum Spix.) 



(Group of Diplodon delodontus.) 



Shell elliptical to subtrapezoidal, inflated, subsolid, with a low pos- 

 terior ridge, sometimes having a slight posterior dorsal wing; one or 

 two central pairs of bars of the beak sculpture usually joining below; 

 pseudocardinals sometimes slightly dentellate. 



Animal having the characters of the genus. 



t DIPLODON DELODONTUS Lamarck. 



*Unio delodonta Lamarck, An. sans. Vert., VI, 1819, p. 77. — *' Delessert, Eec. 

 Coq. Lam., 1841, pi. xii, fig. 7. — *d'Orbigny, Voy. Am. Mer., 1843, p. 605.— 



* Catlow and Eeeve, Conch. Nom., 1845, p. 58. — ""Chenu, 111. Conch., 1858, 

 pi. XII, figs. 1. la. 



* Margarita ( TJnio) delodontus Lea, Syn., 1836, p. 26 ; 1838, p. 20, 



* Unio delodontus Hanley, Test. Moll., 1842, p. J94; * Biv. Shells, 1843, p. 194, pi. 



XXI, fig. 56. — * H. and A. Adams, Gen. Eec. Moll., II, 1857, p. 493. — * Kuster, 

 Conch. Cab. Unio, 1861, p. 234, pi. lxxviii, fig. 5.— *Pj<;tel, Conch. Sam., Ill, 

 1890, p. 1.50. 

 "Margaron ( Unio) delodontus Lea, Syn., 1852, p. 29 ; 1870, p. 46. 



* Unio delodon. Strobel, Mat. Mai., Pt. 1, 1874, p. 71. 



"iUnio lacteolus IjE A, Tr. Am. Phil. Soc, V, 1834, p. 40, pi. viii, fig. 19; * Obs., I, 

 1834, p. 152, pi. viii, fig. 19.—* d'Orbigny, Mag. Zool., 1835, p. 34. 



Argentina; Paraguay; Uruguay; southern Brazil. 



t DIPLODON RHOMBEUS Wagner. 



*Unio rliombeiis Wagner, Test. Fhx7. Bras., 1827, p. 34, pi. xxviii, figs. 1,2. — 



* Hanley, Test. Moll, 1842, p. 208; * Biv. Shells, 1843, p. 208, pi. xxii, fig. 20.— 

 " Catlow and Eeeve, Conch. Nom., 1845, p. 63. — *H. and A.Adams, Gen. Eec. 

 Moll., II, 1857, p. 492.—^ Pjetel, Conch. Sam., Ill, 1890, p. 165. 



"Margarita ( Uiiio) rhombeus Lea, Syn., 1836, p. 39; 1838, p. 25. 

 " Mar gar 071 (Unio) rhombeus Lea, Syn., 1852, p. 38; 1870, p. 61. 



Brazil. 



tDIPLODON PAULISTAvonlhering. 



* Unio paulista von Ihering, Arch, fiir Nat., 1893, p. 93, pi. iv, fig. 7. — * Nehring, 



Jl. de Conch., 1894, p. 82. 



Sao Paulo, Brazil. 



