DIPI,ODON 1233 



''In outline pecnliaris is near to bengalensis (nobis), but in 

 other respects it is very different, having divergent folds on 

 the beaks, a white and thicker nacre, etc. Of all the South 

 American species, with which I am acquainted, it most closely 

 resembles li^ymanii (nobis), but may be easily distinguished 

 by its darker epidermis, its greater inflation and in being a 

 smaller species. There is a slight indication of triplication 

 of the cardinal tooth of the left valve in both the specimens." 



DiPLODON FiRAii^s (Lea). 



"Shell smooth, elliptical, somewhat inflated, very inequilat- 

 eral, rounded before and behind ; substance of the shell rather 

 thick, thicker before ; beaks slightly prominent ; ligament rath- 

 er long and light brown ; epidermis greenish-brown, without 

 rays, with distant marks of growth ; umbonal slope rounded 

 and inflated ; posterior slope narrow, elliptical, and very slight- 

 ly carinate, with indistinct impressed lines in each valve ; car- 

 dinal teeth somewhat thick, compressed and double in both 

 valves ; lateral teeth long, lamellar and somewhat curved ; an- 

 terior cicatrices confluent, rather small and deeply impressed ; 

 posterior cicatrices confluent, large and slightly impressed ; 

 dorsal cicatrices placed in a row across the centre of the cavity 

 of the beaks ; cavity of the shell rather shallow and wide ; cav- 

 ity of the beaks shallow and rounded ; nacre silver-white and 

 very iridescent. 



Length 2.4, height T.4, diam. i in." (Lea). 



Brazil. 

 Unio finniis Lea, Pr. Ac. N. Sci. Phila., X, 1866, p. 33 ; Jl. Ac. 



N. Sci. Phila., VL- 1868, p. 267, pi. xxxiv, fig. 82 ; Obs., XIL 



1869, p. 2y, pi. XXXIV, fig. 82. 

 Margaron (Unio) firmus Lea, Syn., 1870, p. 45. 

 Diplodon firmus Simpson, Syn.. 1900, p. 874. 



"In outline firmus is closely allied to caliginosus (nobis), 

 but it is a heavier species, with a brighter nacre and a less dark 

 epidermis. In the specimens before me the nacre is much 

 worn and the substance of the shell eroded. The beaks are 

 so much eroded that there are no remains of divergent folds, 



