DIPT.ODON • 131 1 



keel extends from the beaks to the hinder end. The cardinal 

 teeth are sublamellar, but quite solid and jagged. The lateral 

 teeth are strongly curved and very long, so that, especially in 

 the left valve, they reach beyond the obtuse postero-dorsal 

 angle. The muscular impressions are deep ; that of the upper 

 anterior retractor lies at the base of the cardinal tooth, that of 

 the under retractor is confluent with that of the adductor. The 

 nacre is white with irregular, oily spots. 



Length 39, height 25.5, diam. 20.5 mm." (von Ihering). 



Vicinity of Rio Doce on the Rio Sao Jose and the Lagoa 

 Jupurana, Brazil. 

 Diplodon garbei von Ihkring, Abh. Senck. Naturf. Ges., 32, 



1910, p. T33, pi. T2, figs. ya-b. 



"The numerous specimens vary considerably in form, ac- 

 cording as the posterior end is round or pointed. Presumably 

 this is owing to sexual dimorphism. The width of the lunule 

 is also subject to considerable variation. The beak sculpture 

 consists of ten or twelve short, radial ridges, of which the 

 seventh and eighth meet at a sharp angle. In proportion to 

 the size of the shell these radial ridges are very short and 

 therefore quickly disappear owing to the erosion of the beaks. 

 The largest examples are from 42-43 mm. long. This species 

 stands quite isolated among the known species of Brazilian 

 Uniones." 



Diplodon hartwrighti von Ihering. 



"Shell of medium size, nearly oval, moderately inflated and 

 rather thin-shelled. Anterior end slightly pointed and regu- 

 larly rounded. The dorsal margin is slightly convex, almost 

 straight, the ventral margin convex, the height being greatest 

 at the last fourth of the length of the shell and from there it 

 ascends to the pointed posterior end. The obliquely truncate 

 posterior end is biangulate by reason of the well-developed 

 posterior ridge. The growth-lines are very close and in the 

 middle of the disk fine and thread-like, becoming wavy and 

 lamellose posteriorly. The beaks are eroded, but the remnants 

 or radial sculpture are visible. Epidermis dark olive-green, 



