4 PROCEEDINGS OF THE NATIONAL MUSEUM vou 71 



Venezuela, December 28, 1925. This locality is in the northwestern 

 part of Venezuela and is drained by the River Portuguesa, which, 

 like almost all streams in Venezuela, is a part of the Orinoco system. 

 This species is related to several other species but seems to stand 

 in a section by itself. The slight swelling on the ventral margin 

 indicates some relationship to the shells of the group A . trigonus Spix, 

 while the radiating rufflings show a resemblance to those of A . tortilis 

 Lea and others of that group. 



MYCETOPODA PITTIERI, new species 



Plate 2 



Shell very elongate, nearly a parallelogram, slightly wider poste- 

 riorly. Dorsal margin straight, rounding into the posterior margin, 

 and forming an angle with the anterior margin. Beaks set far for- 

 ward. Ventral margin nearly straight, passing into the posterior 

 margin in a rounded point and curving regularly into the anterior 

 margin. Posterior ridge low and rounded and posterior dorsal area 

 with faint indications of two radiating grooves. Anterior half of the 

 shell smooth and polished, posterior half dull and smoothish but 

 with minute reticulating periostracal lamellae. Whole surface in 

 front of the posterior ridge with faint radiating striae. Front half 

 yellowish to greenish olive with a very dark edging along the margin. 

 Posterior half brownish. Interior bluish, appearing radiately striate, 

 not very iridescent. All the adductor scars but slightly impressed. 

 Pallial line about 9 millimeters from the margin. Prismatic border 

 rather broad. 



The type. Cat. No. 365227, U.S.N.M., measures: Length, 104.5 

 mm.; height, 35 mm.; diameter, 20.5 mm. 



Dr. H. Pittier obtained the type and two paratypes (Cat. No. 

 365228, U.S.N.M.) at the same locality as the preceding species. 



This species is most nearly related to Mycetopoda pygmaea Spix, 

 from which it differs chiefly in being of much greater size. Its color 

 is different, it lacks the prominent radiating rufflings found on pyg- 

 maea, its posterior ridge is not so sharply defined, and the anterior 

 dorsal line forms a more angular junction with the anterior margin. 

 The two paratypes are almost uniform in size, color, and other details 

 with the type. 



EXPLANATION OF PLATES 



Plate 1 



Figs. 1, 2, 3. Mycetopodella jalcata {Yiiggins) Marshall. Type of the new genus. 

 4, 5, 6. Anodontites guanarensis, new species. Type. 



Plate 2 



Mycetopoda pittieri, new species. Type. 



o 



