4 PROCEEDINGS OF THE U. S. NATIONAL, MUSEUM vol.74 



U.S.N.M., includes a specimen from Rio Tacuari, Department of 

 Cerro Largo, also from Doctor Felippone. 



Despite its greater length as compared with its height, this shell 

 is closely related to the plentiful Aiiodontites patagonicus Lamarck 

 {A. latomarginatus Lea). This relationship is indicated by the 

 very broad prismatic border and the bipartite coloring of both spe- 

 cies. The darker coloring covering the surface from the front to 

 the middle probably indicates the depth to which the shell buries 

 itself in the mud or sand. 



ANODONITES MANSFIELDI. new species 

 Plate 2, figures 1-3 



Shell moderately thick and inflated, subquadrate-elliptic, rounded 

 at both ends, both the dorsal and ventral margin slightly arcuate. 

 Beaks set well forward, about 15 mm. from the anterior end, 50 mm. 

 from the posterior end. Shell rounding from the high middle to the 

 anterior and posterior margins without distinct ridge at either end. 

 Sculpture of well-marked concentric riblets indicating periods of 

 rest in growth. Periostracum smooth and glossy. Color rich, red- 

 dish-chestnut, with two radiating greenish rays on the posterior 

 dorsal area. Interior livid and rose color, the latter color richer in 

 the adductor scars and in the area between the pallial line and the 

 margin. Prismatic border still darker, pallial line about 8 mm. 

 from ventral margin. Anterior adductor scar well impressed, the 

 posterior one lightly impressed. 



The type (Cat. No. 368254, U.S.N.M.) measures: Length, 65 mm.; 

 height, 37 mm.; diameter, 23 mm. It comes from Canada Grande, 

 Department of Cerro Largo, Uruguay, and was presented by Doctor 

 Felippone. 



In color, periostracum, interior features, especially color and in the 

 width of the prismatic border, this shell is related to Anodontites 

 wymami Lea. In form the relationship is not so evident, as Anodon- 

 tites mans-fieldi is subquadrate-elliptic, while Anodontites wymami 

 is ovate, narrow in front, and rather sharply pointed at the rear. 

 The species is named in honor of Dr. W. C, Mansfield, of the United 

 States Geological Survey. 



MYCETOPODA FELIPPONEI, new species 



Plate 1, figure 2. Plate 3, figures 1 and 3 



Shell elongate, oblique, very compressed, much narrowed in front, 

 broad near the rear, and ending in a broadly rounded point at the 

 posterior end, gaping from the point at which the dorsal margin 

 joins the anterior margin to a point behind the middle of the ventral 



