ANODONTITES 



I41I 



This is probably the finest species of the genus. The figure 

 and description by Spix are of a young sheh, not more than 35 

 millimeters in length, but they perfectly fit young shells of 

 Lea's Anodonta caiUiaiidn. It is one of the most nearly or- 

 bicular of the Naiades, being but slightly narrower in front, 

 and often not at all truncate behind. It differs from rubicim- 

 diis in its rounded posterior end and the color of its nacre; 

 from ['adi in its external and internal color. The radial sculpt 

 ture of the nacre is a good distinguishing character. 



Anodontites spixii (d'Orbigny). 



Shell elliptic rhomboid, inflated, rather solid, inequilateral; 

 beaks full and high ; dorsal line arched ; anterior end rounded ; 

 base rounded; posterior slope obliquely subtruncated ; poste- 

 rior ridge rounded, ending in a blunt point a little above the 

 base of the shell : surface with irregular, concentric sculpture, 

 some of it rather coarse, part of it fine and wavy ; epidermis 

 brownish; muscle scars shallow; nacre flesh-colored, with 

 greenish, iridescent tints behind ; pallial line with a small sinus 

 behind ; prismatic border well marked. 

 Length 93, height 68, diam. 47 mm. 

 Rio Parana. 

 Unio (Anodontes) spi.rii d'ORniGNV, Guerin Mag., 1835. P- 39- 

 Glabaris spixii Simpson, Syn., 1900, p. 932. 



In 1835, in the Guerin Magazine, d'Orbigny used the name 

 Unio (Anodontes) spixii d'Orbigny, and stated that it equaled 

 Anodon rotundas of Spix and A. trapeseus Spix, but he gave 

 no description. In the Voyage Amerique Meridionale he re- 

 peated the same statement, but gave a brief Latin description. 

 This description does not agree with either A. rotund us Spix 

 or A. trape:^oideus Spix, which I believe are distinct species, 

 but it does agree fairly with a specimen sent by d'Orbigny 

 to Dr. Lea, labeled by the former "Ano. spixi Orb." While 

 this is close to some other forms of the group, I am inclined 

 to believe that it is a valid species and have used the name 

 apparently applied by d'Orbigny to it. 



