574 PATAGONIAN EXPEDITIONS: ZOOLOGY. 



smoothish, weakly marked with lines of growth. Whorls 5, the first very 

 minute and dark, following whorls strongly convex, the last whorl strongly 

 carinate, concave above and below the carina, convex on the upper sur- 

 face. The base is excavated or concave between the peripheral keel and 

 a second prominent keel which bounds a large, funnel-shaped umbilical 

 area. The aperture is very oblique. Peristome continuous, the outer lip 

 .thin, unexpanded, having small rounded sinuses below the suture, below 

 the peripheral angle, and at the base of the columella. The columella is 

 narrow, very little thickened, straight, much longer than the short, thick 

 parietal margin. 



Length 4.4, diam. 4 mm. 



Montevideo, Uruguay, type in the Museu Paulista, collected by Dr. 

 Florentine Filippone. 



This species has some resemblance to P. hidalgoi, from which it differs 

 by the entirely different shape of the aperture, the swelling between keel 

 and suture, etc. The bisinuate outer lip, the texture and color-pattern of 

 the shell, etc., show it to be a carinate member of the group of P. bisinu- 

 atus. Described and figured from the type specimen. 



POTAMOLITHUS SYKESi Pilsbry. 

 (Plate XLI, Figs. 1-20.) 



Potamolithus sykesi Pilsbry, Nautilus, X, p. 88, Dec., 1896. 



The shell is imperforate, globose-conic, rather solid, yellowish olive, 

 smooth and glossy, faintly marked with growth lines. The spire is conic, 

 truncate at the summit in adult shells of the type lot, about 3^ moder- 

 ately convex whorls remaining. The last whorl is evenly convex, smooth, 

 and expands strongly at the lip. There is a narrow umbilical crescent. 

 The aperture is very oblique and subcircular. The outer lip is strongly 

 expanded, built forward and convex beyond the expansion, and then 

 contracted, with three deep notches in its margin, one near the upper 

 insertion, another median, the third wider and basal in position. The 

 columella and parietal wall are moderately calloused, and the whole 

 peristome is dusky or blackish. 



Length 4.9, diam. 3.9 mm. 



4 " 3-5 " 

 Uruguay River at Paysandu. 



