1913.] NATURAL SCIENCES OF PHILADELPHIA. 667 



developed; location of teeth and general shape characteristic of the 

 genus; beak cavities very shallow, nacre dull bluish-white. 



Length 57, width 25.5, diam. 16.5 mm. 



One complete specimen and four broken valves of this species, 

 which seems to be new, taken in the Rio Jamauchim, were sent from 

 the Goeldi Museum. All of the specimens are more or less damaged, 

 but it seemed best to describe the species from the material at hand 

 on account of the remarkable obsolescence of the hinge teeth. 



Genus ANODONTITES Bruguiere. 



Anodontites ensiformis (Spis). 



Anodon ensiformis Spix. Test. fluv. bras., 1827, p. 31, pi. xxiv, fig. 1. 

 Glabaris ensiformis (Spix) Simpson, I.e., p. 932. 



A single valve was taken at Camp 43, M. & M. R. R. 



Anodontites trapezialis Lamarck, var. anserinus (Spix). 



Anodon anserina Spix, I.e., p. 29, pi. xvii, figs. 1, 2. 

 A single mature specimen taken in the Rio Jamauchim was sent 

 from the Goeldi Museum. 



Anodontites dalli n. sp. PI. XXVII. figs. 1, 2. 



Shell oblong elliptical, rather heavy, moderately full, very inequi- 

 partite; beaks rather low, eroded, but apparently nearly smooth; 

 epidermis moderately dense, chestnut colored, light at the beaks, 

 becoming dark at the margins, very slightly shining; rayless; every- 

 where showing rather distant, low-rounded, concentric growi;h ridges 

 with many fine, wavy, concentric, incised lines between and overlying 

 them; obsolete radiating lines perceptible without a glass over most 

 of the surface ; posterior ridge low, rounded, posterior sulcus shallow 

 and not well defined, much roughened by the growth lines; hinge 

 line nearly straight, about half the length of the shell, with a long, 

 thin ligament, edentulous; anterior margin narrowly and rather 

 evenly rounded, base a long, even curve; posterior margin very 

 obliquely truncate above, sharply rounded below; beak cavities 

 broad and shallow, cicatrices smooth, showing continuous nacreous 

 layers, anterior distinct and well impressed, posterior scarcely 

 defined; nacre silvery -white, iridescent throughout; pallial line 

 distinct. 



Animal unknown. 



Length 77, width 37, diam. 23 mm. 



A single well-preserved specimen of this species, taken on the 

 Island of Mexiana, was sent from the Goeldi Museum. The species 

 is nd^med for Dr. W. H. Dall, of the National Museum. 



