Thalasxohdix.} c;.\sTi;ol'(lA. 



arranged in irregular transverse bands, which slope backwards and 

 form an obtuse angle in the centre. 



Dentition. Button, T.N.Z.I., xiv. 151. p l. 3, f. C, M ; pi. 4. f. I. 



Jaw arcuate, with rounded ends and distant vertical striae. It 

 is membranaceous, soft, and pale-liorn-coloured. There is no median 

 projection. The striations of the jaw appear to arise from folds in 

 the membrane ; it gives the appearance of the jaw being made up of 

 many pieces slightly imbricated. 



The rniluld is | mm. in breadth, with about 70 nearly straight 

 transverse rows of teeth. The formula is 37+1 + 37. with 11 laterals 

 on each side. The central tooth has a single cusp, surmounted by a 

 cutting-point. The laterals are bicuspid, but without an entocone. 

 The outer marginals with much reduced base of attachment, and a 

 long and sharp mesocone. 



Type in the British Museum. 



blab. Rangatira Bush. Temuka (Professor Chilton) : Oxford (ibid.} : 

 Dunedin (Captain Button) ; rnoa swamp at Hamilton's ; Burke's 

 Pass ; Dyer's Pass ; Riccarton Bush (H. S.) ; Owaka (Bryant) : 

 Springburn (Professor Dendy) ; Saddle Hill. Taieri (E. Suter). 



Remarks. Button mentions Napier as habitat, but that is evi- 

 dently a mistake. According to my experience, the species is restricted 

 to the southern half of the South Island. 



Subsp. obnubila, Reeve. 1852. Plate 50, fig. 4. 



Hdix obnubila, RYL-., Conch. Icon., vii, pl. 130. t. 7!>J ; M.H. Viv., iii, <>33 : 

 Hector, Cat. Land Moll. N.Z., 12. Simian (Paryphanta) obnubila, Rve. ; 

 Nomencl. Hel. Viv., 35. Patula obunbii,,. Rve., M.N.Z.M., 9. Thilisso- 

 /uli.i- i</n/f{t<ri obnubila, Rve. : Heclley and Sutor. I'. LS. X.S.W. (2), vii, 

 Suter, T.N.Z.I., xxvi, 127. Helix sigma, Pfr.. M.S. Discus 

 Adams. 



Shell smaller than the species, the spire usually much more de- 

 pressed. and the periphery more distinctly angled. Sculpture and 

 colour the same as in the species. Spire depressed, about one-third 

 the height <>[ the aperture. Proloconch smooth. Whorls 4J. flatly 

 convex, the last generally distinctly angled at the periphery ; base 

 convex. Suture distinct. Aperture oblique. Innately rotund. Pcri- 

 storiK thin, simple, and straight, ('olnnirlln oblique, arcuate. Inner 

 ii/> reflexed above. Umbilicus moderate, deep, about one-seventh 

 of the greatest diameter. 



Din meter Maj.. 9mm. : min.. 8mm. : height. 5mm. 



Animal and dentition the same as in the species. 



Typ< in the British Museum. 



Hob. Near Stonyhurst (F. Suter) ; Riccarton Bush and Dyer's 

 Pass (H. S.) ; Dunedin (Captain Hutton) ; Half-moon Bay, Stewart 

 Island (A. Hamilton). 



