DIPI.ODON 



1239 



are considerably eroded, yet vestiges of radial sculpture re- 

 main. It may be a young shell. It is near siiazidicus, but is 

 less solid and inflated and is smoother and more decidedly 

 trapezoidal. 



Dtpi.oDON LOCEIJ..US (Lea). 



"Shell smooth, elliptical, very much inflated, inequilateral, 

 somewhat rounded before and subtruncate behind ; substance 

 of the shell thin; beaks rather prominent, swollen, with di- 

 vergent folds at the tips ; ligament very small and light brown ; 

 epidermis dark brown, obscurely rayed, with distant marks of 

 growth, striate on the anterior half; umbonal ridge rounded 

 and very much inflated ; posterior slope elliptical, rather wide, 

 with an indistinct furrow in each valve ; cardinal teeth small, 

 very much compressed, very oblique and dou'ble in both valves ; 

 lateral teeth rather small, nearly straight, thin and lamellar; 

 anterior cicatrices confluent and slightly impressed; posterior 

 cicatrices confluent and scarcely visible ; dorsal cicatrices placed 

 above the centre of the cavity of the beaks ; cavity of the shell 

 deep and wide; cavity of the beaks very shallow and rounded; 

 nacre bluish-white and iridescent. 

 Length 1.8, height 1.2, diam. 8 in." (Lea). 

 Argentina. 

 Unio locellm Lea. Pr. Ac. N. Sci. Phila., X', 1866, p. 34; Jl. 

 • Ac. N. Sci. Phila., VI, 1868, p. 264, pi. xxxiii, fig. 79; Obs., 

 XII, 1869, P- 24, pi. xxxiTi, fig. 79. 

 Margaron (Unio) locelliis Lea, Syn., 1870. p. 47. 

 Diplodon locellus Simpson, Syn., 1900, p. 876. 



"Of this well characterized little species there was only a 

 single specimen received. In outline it is near to bengalensis, 

 (nobis), but it is more inflated, has larger teeth and a thicker 

 and white nacre. It differs from ampullae ens, herein describ- 

 ed, in being elliptical, more inflated over the umbones, and 

 being a much lighter shell. The beaks well display the diver- 

 gent folds at the tips, a character so well denoting its South 

 American origin." 



