1262 DIPLODON 



end above it obliquely siibtruncated ; surface apparently finely, 

 concentrically sculptured ; epidermis brownish-green ; teeth 

 compressed ; nacre bluish-white. 



Length 48. height 26. diam. 15 mm. 



Length 50, height 30. diam. 17 mm. 



Peru ; Chile. 

 Unio atratus S()Wi;ki!Y. Conch. Man.. 1839. fig. 148. 

 DipJodon atratus Simpson, Syn., 1900, p. 881. 

 Unto limensis Kitster, Conch. Cab. Unio, 1856. p. 146, pi 



xrji, fig. 7; XLiii. fig. I. 

 Unio jacoha-ns Phiijppt, Mai. Bl.. X\'I. 1869, p. 44. — Pr^Eii-"- 



FER, Nov. Conch.. Ill, 1869, p. 478, pi. cm, figs. 3, 4. 

 Unio landbecki Phiuppi, Mai. BL, X\'I, 1869, p. 45. — Pfeif- 



FER, Nov. Conch.. TIT, 1869, p. 479. pi. cm, figs. 5, 6. 

 Unio diplodon Phiuppi, IMal. Bl., XVI, 1869, p. 46. — Pfeif- 



FFR, Nov. Conch., Ill, 1869, p. 483, pi. civ, 7, 8. 



I have united under the oldest name several of Philippi's 

 so-called species whose dififerences are so trifling that they 

 do not seem to me to be worthy of varietal rank. Philippi 

 bestowed names on every conceivable variation among the 

 Uniones of Chile and it seems to me to be quite likely that a 

 large series of specimens from that region would show that 

 a farther reduction of names was necessary. Those which 

 I have thrown together under the name atratus are rather 

 short and obovate or subrhomboid in outline. Their author 

 does not say whether they are sculptured or not or anything 

 regarding the degree of smoothness of the surface. Unio dip- 

 lodon Philippi may belong here. 



Diplodon optctsu.^ (d'Orbigny). 



"Shell ovate, compressed, rather thick, concentrically ru- 

 gose ; epidermis greenish-brown, umbones smooth, ends ob- 

 tuse, rounded, posterior end elongate ; nacre bluish-green. 



Length 66 mm. In proportion to the length, the height is 

 55-100, the diameter 34-100, length of the posterior margin 

 77-100; a])ical angle 157^.'" (d'Orbigny). 



La Laguna, Province of \^alparaiso. Chile. 



