4 PROCEEDINGS OF THE NATIONAL MUSEUM vol.74 



The type, (Cat. No. 370811, U.S.N.M.) measures: Length, 60 

 mm.; height, about 38 mm.; diameter, if both valves were present, 

 would be about 16 mm. It was collected at Pebas, Peru, by Dr. 

 Harvey Bassler in whose honor the species is named. Kelated to 

 Prodiflodon singeicaldi described in this paper, from which it dif- 

 fers in having the outline elliptic instead of quadrate. It groups 

 also with Frodlplodon paucarpatensis. 



PRODIPLODON PAUCARPATENSIS, new species 



riate 1, flg. 4 



Shell compressed, elongate trapezoidal, slightly narrower in 

 front, slopingly truncated at the rear. Dorsal margin nearly 

 straight, ventral margin nearly straight, rounding into the anterior 

 margin, joining the posterior margin at an angle. Beaks well for- 

 ward, about 18 mm. from extreme anterior end, 56 mm. from ex- 

 treme posterior end. Descent from beaks to anterior margin rather 

 abrupt. Posterior ridge low and rounded. Posterior dorsal area long 

 and broad. Sculpture of well-marked concentric lines of growth. 

 l"ml)onal poition of shell with sculpture evidently similar in general 

 pattern to that of Dlplodoii singewaldl described in this paper, but 

 weathered, so that details can not be pointed out. Tiie whole shell 

 lacks its outer surface and is nearly white. 



The type (Cat. No. 370810, U.S.N.M.) measures: Length, 74 mm. ; 

 height, 39 mm.; diameter, 18 mm. It comes from Paucarpata, on 

 the Maranon Kiver, and was collected by Dr. Joseph T. Singcwald, 

 jr., of Johns Hopkins University. This species has the form com- 

 mon to the well-known Unio complanatus of the United States. It 

 is related to Prod'/ plod on singewaldi Marshall, but differs in form, 

 being more elongate and less oblique. It is related also but not so 

 closely to Prodiplodin hassleri. 



EODIPLODON, new genu^ 



Beaks with very coarse, nearly direct radial undulation, some of 

 which are broken up into nodules. Close to the tip of the beak 

 each pair of undulations unites into a V but the later ones become 

 nearly direct and do not form a V. 



Type of the genus, Kodtplodon gardueme IMarshall.' described 

 below. This genus also is related to the recent genus Diplodon. 



EODIPI.ODON GARDNERAE, new species 



Plate 1, figs. 2, 8 



Shell rather thin, very elongate, beak set very far forward, about 

 7 mm. behind extreme anterior margin, 57 nnn. in front extreme 

 posterior margin. Dorsal margin somewhat broken but evidently 



