1230 DIPLODON 



DiPi.oDON AMi'ULLACEUs (Lea). 



"Shell smooth, oblong, very much inflated, inequilateral, ob- 

 tusely angular behind and rounded before; substance of the 

 shell somewhat thick, thicker before ; beaks prominent and in- 

 flated ; ligament rather small and dark brown; epidermis dark 

 brown, rugosely striate, without rays and with rather distant 

 marks of growth ; umhonial slope rounded and much inflated ; 

 posterior slope elliptical, somewhat carinate, rather wide, ver>' 

 dark brown and with an impressed line in each valve ; car- 

 dinal teeth small, oblique, lamellar and double in both valves ; 

 lateral teeth long, nearly straight, and corrugate ; anterior 

 cicatrices confluent and slightly impressed; dorsal cicatrices 

 placed across the cavity of the beaks ; cavity of the shell deep 

 and rounded ; cavity of the beaks very shallow and rounded ; . 

 nacre white and iridescent. 



Length 2.5, height 1.5, diam. i.i in." (Lea). 



South America. 

 Unio anipuJlacens Lea, Pr. Ac. N. Sci. Phila., X, 1866, p. 34 ; 



Jl. Ac. N. Sci. Phila.. VL 1S68, p. 269, pi. xxxv, fig. 83; 



Obs., XTI, 1869, p. 29, pi. xxxv, fig. 83. 

 Margaron (Unio) ampuUaceus Lea, Syn., 1870, p. 53. 

 DipJcdon ampuUaceus Simpson, Syn., 1900, p. 874. 



■'A single specimen only of this species was received. The 

 beaks are much eroded, but still an indistinct indication re- 

 mains of the divergent character of the tips. In outline it is 

 closely allied to mcxicanus Phil., but differs entirely in the 

 teeth and the color of the nacre. It is also very near to char- 

 rnanns d'Orb.. but is more inflated and not so wide. It re- 

 minds one of hJandingianns (nobis), but is more quadrate than 

 that shell and more oblique. In the specimen before me there 

 are slightly impressed lines running from the beaks to the 

 anterior half of the margin, which give the surface a rugose 

 character. There is also a slight emargination at the posterior 

 basal margin, which may not pertain to all other specimens." 



DiPT.ODON wymanii (Lea). 



Shell large, .subrhomboid, solid, subinflated, inequilateral, 

 with moderately full, slightly raised beaks having uneven, 

 radial sculpture: posterior ridge high, rounded, ending in a 



