6 PEOCEEDINGS OF THE NATIONAL MUSEUM vol. 77 



by the two thin, platelike pseudocardinals of the right valve. 

 Lateral teeth of left valve long, subequal. The lateral tooth of 

 right valve loang, thin, rather high. Prismatic border a m^re 

 edging. 



The type (Cat. No. 380554, U.S.N.M.) measures: Length, 63 mm.; 

 height, 33 mm.; diameter, 21.5 mm. It and three younger paratypes 

 (380756) come from Rio Yaguaron, Department of Cerro Largo, 

 Uruguay, and were presented by Dr. Florentino Felippone. 



The species is closely related to Diplodon pilshryi Marshall, but is 

 smaller, less pointed at the rear, and more nearly elliptic. The Rio 

 Yaguaron flows into the Laguna Merim and forms most of the bound- 

 ary between the Department of Cerro Largo, Uruguay and the 

 State of Rio Grande do Sul, Brazil. The type locality of Dijjlodon 

 pilshryi is Canada Grande, the water of which also reaches Laguna 

 Merim through the Rio Tacuary. The two species are thus geo- 

 graphically related as coming from the eastern drainage of Uruguay. 



ANODOTITES PALrJERI, new species 

 Plate 2, Figures 1, 4, 7 



Shell rather thin, elongate, somewhat oblique, wide at the rear, 

 much narrower in front. Dorsal margin lightly arched, ventral 

 margin nearly straight, joining the posterior margin in a rounded 

 point, and gently curving into the ventral margin which is abruptly 

 rounded. Beaks set about 15 mm. behind the extreme anterior end 

 60 mm. in front of extreme posterior end. Posterior area with a 

 low rib running from the beak to lower portion of posterior margin. 

 Posterior ridge rounded, anterior ridge not differentiated from gen- 

 eral surface. Anterior half of surface smoothish, with a dull 

 unctuous polish; posterior portion with innumerable concentric 

 lamellae of fugacious periostracum ; concentric sculpture of many 

 fine growth striae. Across the portion just in front of the middle 

 are several puckered bands radiating from the beak to the ventral 

 margin. Under compound microscope the periostracum shows the 

 very fine radiating sculpture usual to the genus ^. Color of surface 

 uniform chestnut. Interior in poor condition, evidently iridescent, 

 bluish, and flesh-colored. Sinulus triangular, prominent. Cavity 

 of shell shallow. Adductor scars well impressed. Pallial line well- 

 marked, about 8 mm. from the ventral edge. Prismatic border very 

 narrow. 



The type (Cat. No. 380695, U.S.N.M.) measures: Length, 75 mm.; 

 height, 42 mm. ; diameter, 24 mm. It comes from a small stream, in 

 a dense jungle, 13 kilometers south of Puerto Santos, Province of 



2 Marshall, Microscopic Sculpture of Pearly Fresh-Water Mussel Shells : Proc. U. S. Nat. 

 Mus.. vol. 67 No. 2576, art. 4, 1925, pp. 1-14, pis. 1-A. 



