DIPLODON 1 26 1 



this might be distinguished from nearly alHed forms. Sower- 

 by's Unio auratus seems to be a yoimg shell of the same thing. 

 Its beaks are perfect and therefore a little higher than those 

 of the specimens figured by Philippi, which are eroded, and 

 vSovverby's shell shows more scattered rays. 



DiPLODON MOD£;sTus ( Kuster) . 



Shell oblong, subtrapezoid, subinflated, subsolid, inequilat- 

 eral ; beaks low, their sculpture not seen; surface apparently 

 strongly, concentrically striate ; posterior ridge rounded, end- 

 ing behind in a blunt point on the nearly straight base line ; 

 epidermis fuscous, shining ; pseudocardinals subsolid ; laterals 

 short ; nacre bluish-white. 



Length 58, height 32, diam. 20 mm. 



Chile. 

 Unio modcstns Kustkr, Conch. Cab. Unio, 1856, p. 147, pi. 



xijii, fig. 2. 

 Diplodon modestus Simpson, Syn., 1900, p. 881. 

 Unio ianthinus Philippi, Mai. Bl., XVII, 1869, p. 47. — PPKiF- 



i^KR, Nov. Conch.. Ill, i8(.>9, p. 485, pi. civ, figs. 11, 12. 

 Unio valdivanus Phiijppi, Mai. Bl, XVI, 1869, P- 4^- — Pfeif- 



FRR, Nov. Conch., Ill, 1869, p. 479, pi. cm, figs. 7. 8. 

 Unio montanus Pktijppi, Mai. BL, XVI, 1869, P- 4^- — Pfeif- 



FF.R, Nov. Conch., Ill, 1869, p. 482, pi. civ, figs. 3, 4. 



Credited to Charpentier manuscript by Kuster. 



At the time of writing the Synopsis I was inclined to believe 

 that this species equaled some of Philippi's Chilean species, 

 but more careful study of the figures and descriptions lead 

 me to believe it is dififerent. It seems to be rather more solid 

 and inflated like the forms, which were placed by Philippi 

 under D. ianthinus. A dorsal view of Charpentier's species 

 shows that both ends are suddenly narrowed into blunt points. 



Diplodon atratus (Sowerby). 



Shell rather short, obovate, subrhomboid, subcompressed, 

 scarcely subsolid. inequilateral, with slightly raised beaks hav- 

 ing delicate, radial sculpture ; posterior ridge low, rounded, 

 ending in a rounded point behind near the base, the posterior 



