DIPLODON 1229 



Unio rhombcus Wagnrr, Test. Fluv. Bras., 1827, p. 34, pi. 



XXVIII, figs. I, 2. — HanIvEy, Biv. Shells, 1843, P- 208, pi. 



XXII, fig. 20. 

 Margarita (Unio) rJwnibeus LiiA, Syn., 1836, p. 39; 1838, p. 



25- 

 Mari^aron (Unio) rhombeus Lea, Syn., 1852, p. 38; 1870, p. 



61. 

 Diplodon rhombeus Simpson, Syn., iqoo, p. 873. 



"The form of this species differs greatly in the height of 

 the beaks. It is distinguished from Unio perm'ianns Lam. 

 by being neither plicate nor angulate." 



Diplodon pauijsta (von Ihering). 



"Shell silicate, elliptical, inequilateral, rounded in front, pos- 

 • teriorly obtusely angulated and rounded. Not very thick ; 

 beaks rather low, with undulating, radiate folds on the ante- 

 rior and posterior slopes near the apices. Epidermis green or 

 brownish-green, without rays. Cardinal teeth lamellar, thick; 

 laterals rather long, curved, or nearly straight. Nacre bluish- 

 white either dull or iridescent. 



Length (males) 48-51, height 59-60, diam. 31 mm. 



Length (females) 54-57, height 61-65, diam. 32-35 mm. 



The beaks are situated at from .22 to .26 of the length and 

 the hinge at from .64 to .y2 of the length." (von Ihering). 



Sao Paulo, Brazil. 

 Unio paulista von Ihering. Arch, fiir Nat., 1893, p. 93, pi. iv, 



Diplodon paidista Simpson, Syn., 1900, p. 873. 



''Unio paulista differs from U. coriaceus Dkr. resp. multi- 

 striatus Lea, in the less wrinkled and bright green epidermis 

 and in the low development and granulation of the secondary 

 radial striae. U. psanimactinus Bronn is a similar species, but 

 in that the epidermis is a darker olive-brown with stronger 

 growth-lines and the numerous, fine, radial striae spread down 

 widely over the posterior slope and the umbonal fold. Finally 

 this species is also related to U. greeffeanus, but that species 

 is larger, with a darker epidermis, without granulation in front 

 of the beaks and with less sharply marked sexual dimorphism." 



