ortmann: south American naiades. 527 



Diplodon wagncnanum Simpson, 1900, p. 877; 1914, p. 1240. 



Type-localitij. Rio San Francisco (Wagner). 



Other Localities. — Rio Parahylm do Sul, Rio de Janeiro (Von Ihcring, 1893, p. 

 115); Rio Santa Maria, Espirito Santo (Von Ihering, 1910, p. 134) (drainage of 

 Rio Doce). The form from tlie latter locality has been named var. santanus Von 

 Ihering. 



Rio Piracicaba, Sao Paulo, and^Rio Tamanduatahy, Sao Paulo (Von Ihering). 

 The latter two localities are somewhat doubtful, since the specimens are not exactly 

 like ellipticiis. The location and drainage of the last named river is unknown to 

 me. 



In the Carnegie Museum is one specimen, labeled "Brazil" (Holland Collec- 

 tion). Not quite typical. 



The change of the specific name ellipticus to umgnerianus is unwarranted. 

 Spix gave the name in the plate in connection with the generic name Diplodon. 

 Since the latter stands, the specific name also is entitled to recognition. 



In spite of Von Ihering's re-description of the type, this species is as yet poorly 

 knowii, and our knowledge of it is founded chiefly upon what Von Ihering has 

 said. The species is i)ositively known from the Rio San Francisco and the Rio 

 Parahyba do Sul; the other localities are more or less doubtful, since the specimens 

 described from them do not fully agree with the type. Those from the Rio Santa 

 Maria have been distinguished as a variety. 



AU we can gather from descriptions and figures is that D. ellipticus is a sub- 

 elliptical or subtrapezoidal shell, of dark green to blackish color, with rather smooth 

 surface. It has in the anterior part of the shell a shallow depression, often producing 

 a shallow emargination in the anterior part of the ventral margin. In outline, 

 the shell is distinctly olilique, narrower in front, higher behind. The beak-sculpture 

 consists of simple, fine radial bars, which are rather short, and somewhat cut up 

 on the posterior slope by irregular, oblique wrinkles. The nacre is blueish white. 

 Pseudocardinals somewhat compressed, but not thin, crenulated, two in right, 

 one in left valve, but the latter with an angle at its base, representing the remnant 

 of a posterior tooth. 



Our specimen from Brazil was received as ellipticus. It agrees in most of the 

 above characters, except that it is shorter in proportion to height, with less pointed 

 posterior end. Also the projection of the lower margin is indistinct. The beak 

 has eleven radial bars in front of the posterior ridge, the seventh and eighth meeting 

 in the middle. On the posterior slope there are corrugations and fine, oblique 

 ridges. L. 32 mm.; H. 21 mm.; D. 12 mm. This specimen might very well be 



