BY HENRY SUTER. 489 



whorl not descending. Aperture slightly oblique, lunar, rather 

 considerably excavated by the penultimate volution. Peristome 

 straight, acute, margins very little approximating. Columellar 

 margin short, oblique, slightly tliickened and reflexed. Base 

 convex, with a thin white callosity to a short distance outside the 

 aperture. Umbilicus very narrow, open, deep. 



Diam., greatest 3-J, least 2f ; height 2 millm. 



Animal unknown. 



Hah. — Wairoa Gorge, near Nelson. 



This species is nearest to A. venulatus, Pfeiffer, but is dis- 

 tinguished from it by being smaller, perforated, and the ribs 

 more distant. 



Allodiscus Urquharti, n.sp. 



(PI. XXII. figs. 4:-4:d.) 



Shell very minute, globosely depressed, umbilicated ; colour 

 horny without any markings, silky, thin, and fragile, transparent, 

 with extremely fine and close set radiate ribs, which are slightly 

 directed forwards and reach to the umbilicus ; ribs about 40 per 

 millm. Spire short, convex. Apex blunt, smooth. Whorls 3J, 

 narrow, slowly and regularly increasing, rounded, the last not 

 descending. Suture deep ; periphery rounded. Aperture nearly 

 vertical, rotundly lunate, much excavated by the penultimate 

 whorl. Peristome simple, straight, acute, columellar margin 

 regularly arched, not reflexed ; margins convergent. Base 

 rounded. Umbilicus narrow, previous deep. 



Diam., greatest IJ, least 1 J ; height 1 millm. 



Hab. — North Island : Pirongia Mt. (A. T. Urquhart), Hunna 

 Range (Capt. T. Broun). 



I have much pleasure in naming this rare species after Mr. A. 

 T. Urquhart, who first discovered it. 



A. Urquharti is the minutest, widest umbilicated, and closest 

 ribbed known species of the section Allodiscus. 



Jaw (fig. 4c) arcuate, consisting of about 14 thin plaits, indent- 

 ing both margins. The central plaits are broader than those on 

 the ends, and are separated from each other by a narrow interstice. 



