690 GASTROPODA. [P'ulmonato- 



KBY TO SPECIES. 

 A.. Riblets about 12 per millimetre; parietal wall with 7 lamellae leiodvn. 



B. Riblets about 15 per millimetre. 



a. Narrowly perforated. 



b. Parietal wall with 2 lamellae, the lower one stout . . ureweraensi*. 

 bb. Parietal wall with 3 equal lamellfe . . . . pseudoleiodon. 



aa. Umbilicus one-fourth of greatest diameter : parietal wall 



with 1 emarginate lamella . . . . . . aorangi. 



iinn. Umbilicus one-third of greatest diameter. 



/;. Parietal wall with 5 lamellae, the uppermost stronger, 



. emarginate . . . . . . . . Heclori, 



bb. Parietal wall with 3 lamellie. fin- i:ji|" ; 'most stronger, 



emarginate . . . . . . . . huniiaensis. 



bbb. Parietal wall with 5 simple lamella?, the four lower 



ones close together . . . . . . . . wairarapa. 



C. Riblets about 25 per millimetre; umbilicus one - third of 



greatest diameter. 



a. Parietal wall with 1 simple lamella . . . . . . Chiltoni. 



aa. Parietal wall with 1 emarginate lamella . . . . microundulata 



D. Riblets about 30 per miDimetre ; outer wall with 8 lamella? . . minuta. 



1. Endodonta aorangi, Suter. 1890. Plate 27. fig. 4. a. b. 



Helix aoran-'/i. Sut., T.. X.X.I., xxii, 1889 (1890), 223, pi. 14, f. 5, a-c. Patula 

 (Maoriana) aorangi. .Sut.: I'ilslnx. Alan. Conch. (2), viii, 90, pi. 24, 

 f. 48-51; ix, pi. 4, f. 30-32. i';:<l"<L>n1a (Ptychodon) aorangi, Sut.: 

 Hedley and Suter, P.L.S. N.S.W. (2). MI. 653; Suter. J. de Conch., 

 xli, 260. 



Shell minute, depressed, umbilicate, finely costate, thin, not sliining. 

 Sculpture consisting of radiate nearly straight riblets, about 15 per 

 millimetre, closer together on the protoconch ; interstices \vith minute 

 and numerous lines of growth. Colour yellowish-white, with some- 

 what irregular chestnut zigzag or sinuated streaks. Spire but little 

 elevated, broadly convex. Protocoiich of 1J convex volutions. Whorls 

 5 to 5|, slowly increasing, rounded ; periphery and base convex. 

 Suture impressed. Aperture slightly oblique, rotundly lunar, within 

 with 12 laminae 1 on the parietal wall a little above the middle, 

 fairly stout, emarginated above by a deep groove ; 2 stout tongue- 

 shaped laminae, connected at the base, on the columellar lip, the upper 

 shorter and sharp, the lower high and blunt ; 9 thin and slender long 

 lamellee on the outer wall, the four upper ones separated from the 

 lower by a somewhat larger interspace. Peristome straight, acute, 

 margins slightly convergent. Columella very short, oblique, arcuate, 

 lip not reflexed above. Umbilicus deep, perspective, about one-fourth 

 of the greatest diameter. 



Diameter, 2 mm. : height, 1-25 mm. 



Dentition. SvteT, T.N.Z.I., xxiv. 300, pi. 23, f. 51, 52. 



Jaw arcuate, narrow, slightly tapering at the ends, with about 10 

 distant vertical stri;<\ 



Radula having the formula 90x10+7+1+7+10. Central and 

 lateral teeth tricuspid : marginals tricaispid, the. outer ones with "2 

 cusps only. 



