DIPLODON" I 27 I 



Group of Diplodon burrougliianus. 



Shell elliptical, moderately solid, inflated, sharply pointed 

 behind, with a high, well-developed posterior ridge ; beaks 

 rather full ; the sculpture consisting of regularly radiating, 

 widely separated, sharp ridges, the intervening grooves round- 

 ed out ; epidermis smooth, dark olive with lighter bands ; pseu- 

 docardinals compressed, rough, vertically ridged, usually trifid 

 or quadrifid in each valve ; laterals curved, compressed ; mus- 

 cle scars smooth ; nacre white, silvery. 



Animal unknown. 



DiPLODON CUKROUGHIANUS (I.ea). 



Shell ovate, subinflated, rather solid, inequilateral, with full 

 but not elevated beaks, whose sculpture consists of strong, un- 

 even, radial ridges ; posterior ridge well developed, angular, 

 ending behind in a point on the median line ; surface sculp- 

 tured with irregular, strong, concentric ridges, and having 

 traces of radial sculpture ; epidermis ashy-green and dark brown 

 in alternating, concentric bands ; left valve with two compress- 

 ed, roughened pseudocardinals, the posterior small, and two 

 curved laterals ; right valve with two pseudocardinals, the 

 upper small, and one lateral ; hing"e line narrow and rounded 

 between the two sets of teeth ; muscle scars shallow ; nacre sil- 

 very, iridescent behind. 



Length 88, height 58, diam. 35 mm. 



Length 71, height 43, diam. 26 mm. 



Parana River, South America. 

 Unio burroughianns Lka, Tr. Am. Phil. Soc, V, 1834, p. 67, 



pi. X, fig. 27; Obs., L 1834, p. 179, pi. X, fig. 2y. — Hanley, 



Biv. Shells, 1843. p. 197, pi. xxri, fig. 2. — Sowerby_, Conch. 



Icon., XVI, 1866, pi. XXXII, 169. 

 Margarita (Unio) biirronghianus Lea, Syn., 1836, p. 29; 1838, 



p. 21. 

 Margaron (Unio) bnrroiighianu.s Lea, Syn., 1852, p. 31 ; 1870, 



p. 50. 

 Diplodon burrougliianus Simpson, Syn., 1900. p. 883. 



