■ ' DIPI.ODON 1259 



A rather sliort. inHated, solid species, but from the figure 

 I should say it was a member of the granosus group. I have 

 never seen the shell. 



DiPi.oDON GAssiK.si (Kuster). 



Shell subrhomboid, subsolid, a little narrower in front, com- 

 pressed or subcompressed, inequilateral ; beaks probably low 

 but so eroded in the specimens seen that their characters can 

 not be made out ; posterior ridge scarcely developed, widely 

 rounded ; dorsal line curved, ending behind in a rounded point 

 at the base : base line straight or a little curved ; surface with 

 fine, irregular growth lines ; epidermis dark, olive or bronzy- 

 green, a little darker on the posterior slope ; left valve with 

 two pseudocardinals, the anterior higher and subcompressed, 

 the posterior low and imperfect, with two delicate, curved lat- 

 erals, the upper the smaller; right valve with two compressed 

 pseudocardinals, the upper small, and one lateral ; anterior 

 scars impressed ; posterior scars superficial ; nacre bluish-white, 

 darker and blotched in the cavities, considerably thicker in 

 front. 



Length 52, height 28, diam. 15 mm. 



Chile. 

 Unio gassiesi Ki'stek, (part). Conch. Cab. Unio, 1856, p. 148, 



pi. XI.III, fig. 4. 

 Diplodon gassiesi Simpson. Syn., tqoo. p. 881. 

 ? Unio auratus Reeve. Conch. Icon., X\"I, 1865, pi. xxix, fig. 



150. 



The younger shells of this species are slightly rounded 011 

 the basal line ; the old shells become developed at the posterior 

 end, which grows downward until the base line is straight. 

 The nacre is thickened in front and lurid in the cavities ; the 

 posterior pseudocardinal of the left valve is low and feebly 

 developed. 



Diplodon aplatus (Reeve). 



Shell oblong, subrhomboid, convex, subsolid, inerpiilateral ; 

 dorsal line irregularly curved, ending behind at the base in a 

 wide sulitruncation or broad rounded point ; posterior ridge 



