psEUDorjQN 1083 



From a study of material of what I believed was P. pcguen- 

 sis and crebristriatns in the National Museum I came to the 

 conclusion that both were of the same species. Further study 

 inclines me to doubt whether the P. pcguensis is genuine. The 

 crebristriatns seems to be a smaller, more compressed form, 

 more strongly sculptured, and having less inflated beaks than 

 P. pegitcnsis. 



Var. curvatns Preston. 



"Shell having the ventral margin more curved and generally 

 less ovate in shape than in the typical form." (Preston). 



Type locality, Pegu. 

 Pseudodon crebristriatns var. curvata Preston, Rec. Ind. 



Mus., VII, 1912, p. 295. 



Pseudodon peguensis (Anthony). 



Shell smooth except on the posterior slope, which has 

 broad, rugose folds, subrhomboid, somewhat narrower in 

 front, inequilateral, subinflated, solid ; beaks full and high, the 

 umbonal region broad ; posterior ridge more or less double, 

 ending in a wide, feeble biangulation ; base line curved, a lit- 

 tle fuller behind the middle ; anterior end rounded ; dorsal 

 .slope obliquely subtruncate ; epidermis dark brown or nearly 

 black ; pseudocardinals prominent and slightly bilobed, par- 

 ticularly in the right valve : anterior scars distinct, deep ; pos- 

 terior scars confluent ; dorsal scars deep ; nacre light salmon, 

 iridescent. 



Length 93, height 60, diam. 30 mm. 

 Burma; Pegu. 

 Monocondylcca pcguensis Anthony, Am. Tl. Conch., I, 1865, 



p. 205, pi. xviii, fig. 2. 

 Mar gar on (Monocondykva) pcguensis Lea, Syn., 1870, p. 73. 

 Trigonodon crebristriatum var. pcguensis Hanley and Theo- 

 bald, Conch. Ind., 1876, p. 5, pi. ix, fig. 5. 

 Pseudodon crebristriatns var. pcguensis Simpson, Syn., 1900, 



p. 835. 



Specimens in the National Museum from Pegu labeled 

 Pseudodon pcguensis are probably P. crebristriatns, but they 



