1899.] NATURAL SCIENCES OF PHILADELPHIA. 393 



subcircular, nearly closed by the large teeth ; peristome reflexed, 

 continuous in a raised callus across the jiarietal wall. Teeih : 

 parietal fold a large, sinuous tongue-like process, the lower ramus 

 of which is erect, the upper one rising in a point where it joins the 

 upper termination of the lip, the space between the branches 

 concave; outer lip bearing a strong, concave, callous rib, ending 

 below in a compressed tooth; basal margin bearing a similar com- 

 pressed tooth, extending outward on the lip, and separated from 

 that on the outer lip by a deep sinus. 



Alt. 4, diam. 10 mm. ; greatest width of the umbilicus 3 2 mm. 



Topo Chico, near Monterey, State of Nuevo Leon, Mexico. 



Closely allied to P. implicata Beck, with which it agrees in the 

 general form and the armature of the aperture. It differs from 

 implicata in the strongly ribbed surface, less convex base, de- 

 cidedly narrower central umbilical opening and greater deviation 

 of the last whorl, which differentiates the median opening from 

 the rimation much more sharply than in P. impUcaia. 



P. rhoadsi differs from P. oppllata in being larger, with differ- 

 ent sculpture and narrower umbilicus. 



Polygyra suprazonata n- sp. 



Shell depressed subglobose with low conoid spire and very narroAV 

 though deeply perforating umbilicus, somewhat enlarged at its 

 opening; glossy, slightly wrinkle-striate, finely malleated in places; 

 reddish brown, paler around the umbilicus and with a wide whitish 

 band above the periphery. Whorls 5^, those of the spire slowly 

 increasing, the last wider, double the width of the preceding 

 whorl, abruptly deflexed in front, rounded at the periphery and 

 beneath, deeply constricted behind the lip. Aperture oblong, very 

 oblique, with reflexed, white peristome; parietal fold a rather small 

 oblique lamina recurved in a very short branch above ; outer lip 

 with a small tooth, above which there is a strong concave rib; 

 basal lip bearing a small compressed tubercle and a slight thicken- 

 ing to the left of the tubercle. 



Alt. 6.5, diam. 12 mm.; width of umbilicus 1.5 mm. 



Alt. 5.7, diam. 10.2 mm.; width of umbilicus 1 mm. 



Tzintzuntzan, State of Michoacan. 



This is one of the largest Mexican species. It is allied to P. 

 chiapensls (Pfr.) and P. matermontana Pils., differing from the 



