PILSBRY: non-marine MOLLUSCA of PATAGONIA. 585 



shells this is often scarcely noticeable. The base tapers and is not very con- 

 vex. The suture descends very slightly in front. There is an extremely 

 narrow umbilical area. The aperture is oblique and ample, angular above. 

 The outer lip is thin and acute, and forms a half-circle. The columella 

 is very heavily calloused, its face flat or excavated, with a longitudinal 

 depression. Parietal callus heavy within, thin and adnate at the edge. 

 Length 3.5, diam. 3.4 mm.; length of aperture 2.7 mm. 

 Rio Ribeira, Yporanga, State of Sao Paulo, Brazil. Types collected 

 by R. von Ihering, 1908. 



This form resembles P. lapiditm (d'Orb.) in shape, but differs by its 

 very broad columella and diminutive size. It is rather closely related to 

 P. biischii, though differing by the rounded periphery, which even in im- 

 mature shells shows the hardly noticeable trace of an angle. P. iiityacal- 

 losiis is an allied species. 



A series of eight shells from Hiririea, Rio Ribeira, State of Sao Paulo, 

 collected dead, but not bleached, has been submitted by Dr. von Ihering. 

 The cuticle is olive-green or clear green. The shape is about as in ribeir- 

 ensis. In several shells there is a very narrow umbilical area, defined by 

 a raised line. In the youngest shells, diam. 2 mm., the columella is ver>' 

 wide, as in nbeirensis, but in the largest shells, length 5.2, diam. 4.2 

 mm., it is quite noticeably narrower. In one shell of this lot (Plate 

 XLI^, fig.''^4r) there is a wide, lunate, concave umbilical area, defined 

 by an acute black keel, the columella being wide, as in P. ribeirensis. It 

 measures, length 4.2, diam. 4 mm. Further material is needed to show 

 the status of this form, which for the present may be considered a race of 

 P. ribeiroisis. 



POTAMOLITHUS CATHARIN/E Sp. nov. 



The shell is perforate, acutely ovate, solid but strong, covered with an 

 olive-green cuticle. The spire is conic, its lateral outlines straight, the 

 apex small, but somewhat obtuse, entire in adult shells. Whorls s% . evenly 

 convex, parted by an impressed suture, which descends very briefly at the 

 aperture. The last whorl is strongly convex throughout ; near the aper- 

 ture it dilates a little. The aperture is slightly oblique, ovate, fleshy- 

 gray within, blue-white near the lip. The outer lip is thin and black at 

 the edge, and with the basal lip forms a half-circle ; in profile its edge is 

 even. The columella is heavily calloused, the callus extending across the 

 parietal wall, where it is less thickened. There is a distinct umbilical 



