38 THE NAUTILUS. 



a solid cherry-brown to white, and when lined there is a wide varia- 

 tion in the number of lines. 



NEW LAND AND FRESH-WATER SHELLS FROM MEXICO. 



BY H. A. P1LSBRY AND A. A. HINKLEY. 



POLYGYRA POI.ITA n. Sp. PL 5, fig. 11. 



The shell is narrowly perforate, with a rather long rimation, dis- 

 coidal, the spire very slightly convex; whitish corneous (probably 

 partially bleached), glossy, with faint sculpture of weak growth lines 

 only. The whorls increase slowly ; the last one is rounded at the 

 periphery and descends abruptly at the aperture ; it is constricted 

 and opaque white behind the lip, and there is a short oblique groove 

 within the umbilicus. Aperture very oblique. The peristome is 

 thick, expanded outwardly, reflexed below, the ends connected by a 

 rather thick callus, which bears a rather long, obliquely V-shaped 

 tooth, the upper branch of which, though not so high as the lower, 

 is well developed and connects with the peristome. There are two 

 strong lip teeth, the upper one peripheral in position, tubercular, the 

 lower one basal, compressed, entering across the lip-callus ; a low, 

 rather sharp lip-callus, more immersed at its lower end, is above the 

 upper tooth. 



Alt. 4, diam. 9.6 mm.; width of umbilicus 2.6 mm.; whorls 5. 



Tampico, in river debris, coll. by A. A. Hinkley. 



This species closely resembles P. texasiana hyperolia Pils. and 

 Ferr., but it differs by the wider constriction or furrow behind the 

 peristome, and the decidedly more deeply immersed upper lip tooth. 

 The umbilical rimation is also longer than usual in that form. 



POLYGYRA AULACOMPHALA n. Sp. PI. 5, fig. 12. 



The shell is very narrowly perforate, with a rather long rimation, 

 subdiscoidal, with low spire ; whitish corneous (probably bleached), 

 glossy, faintly, finely striate above, smoother below, where faint 

 traces of spiral striae are visible. Whorls slowly increasing, the first 

 projecting slightly, the last rounded peripherally, descending a little 

 in front, constricted behind the outer and basal margins of the peri- 

 stome, with shallow pits in these positions. A long, deep furrow on 



