ART. 12 NEW LAND AND FRESH-WATER MOLLUSKS MARSHALL 9 



iridescent posteriorly, thicker in front, an obscure sulcus showing 

 the location of the posterior ridge. Anterior adductor scars very 

 deep ; posterior scars well marked but shallow. In the right valve 

 there are two pseudocardinal teeth which are parallel to each other, 

 the outer one the smaller, the inner one transversely subdivided near 

 the beak. In the left valve there is one pseudocardinal divided into 

 three parts, the middle part being small. All the pseudocardinals 

 are strongly striated vertically and the summits are crenulated. 

 Lateral teeth long and slightly curved and obliquely striated; the 

 single one in the right valve being obsoletely vertically striated. 

 The outer one of the two laterals in the left valve is the smaller. 

 Pallial line well impressed, 4 to 5 mm. from the margin. Prismatic 

 border a mere line. 



The type, Cat. No. 361959, U.S.N.M., measures : Length, 40 mm. ; 

 height, 25 mm. ; diameter, 18.5 mm. It comes from the Paraguay 

 River at Asuncion, Paraguay, and was presented by Dr. Florentinu 

 Felippone. It classifies between D. hurroughiana Lea and D. trifidus 

 Lea, but is more nearly related to the latter. It differs from trifidus 

 in being much less nasute, in being less elongate and more inflated, 

 in color, which in trifidus is greenish while in asuncionis it is uni- 

 formly rich chestnut, and in having the posterior ridge much less 

 sharply angled. In beak sculpture the two species are very similar, 

 but in asuncionis it is stronger and the posterior dorsal area near the 

 beaks has five fine, elevated, sharp lines. In asuncionis the lateral 

 tooth of the right valve is single as it normally is in the Naiades; 

 but in trifidus it is divided lengthwise into three parts, the middle 

 part being large and similar to the usual lateral tooth, the inner 

 being much lower and nearly as long as the middle part, the outer 

 part very small and only about half the length of the middle part. 

 This divided lateral probably suggested the name trifidus. The type 

 seems to be the only specimen of trifidus ever found, and it may be 

 that the divided lateral is an individual character. 



DIPLODON (CYCLOMYA) SMITHI. new species 

 Plate 2, figs. 1,7; plate 3, fig. 6 



Shell compressed, rather thin, subquadrate, narrower and rounded 

 in front, broad and obliquely truncate in the rear. Surface nearly 

 evenly rounded, with but little convexity and lacking a clearly 

 defined posterior ridge. Posterior area rounding up gently and 

 anterior area more abruptly into the middle portion of the shell. 

 Most of the shell, excepting the anterior and posterior areas, with 

 obscure, coarse, radiating lines similar to those in D. felipponei 

 Marshall, D. funehraJe Lea, I). pateUoides Lea, and others of that 

 group. Beak sculpture consisting of 12 coarse, radiating ribs, the 



