660 GASTROPODA. [P-iliii<>i<atri. 



Type in the Canterbury Museum, Christchurch. 



Hob. Auckland, type (Cheesernan) ; near North Cape (C. Cooper) ; 

 Whangaroa (C. Traill) ; Whangarei (Musson) ; Waiheke Island ; Swan- 

 son (H. S.) ; Mount Wellington lava-fields (Musson) ; Hunua Range 

 (Major Broun) ; Tuakau ; Ohaupo (Musson) ; Mount Pirongia (T. 

 Urquhart) ; Toko, near Stratford (R. Murdoch). Not known from 

 the South Island. 



6. Therasia Thaisa, Button, 1883. Plate 50, fig. 10. 



Therasia Thaisa, Hutt., N.Z.J.S., i, 477; T.N.Z.I., xvi, 1883 (1884), 182, 

 202 ; Hedley and Suter, P.L.S. N.S.W. (2), vii, 641. Geronlia (Therasia) 

 Thaisa. Hutt. : Pilsbry, Man. Conch. (2), viii, 70. Flammulina (Therasia) 

 Thaisa, Hutt, : Pilsbry, I.e. (2), ix. Hi. pi. 3, f. 14-16 ; Suter. J. de Conch., 

 xli. 24H. 



Shell depressed, umbilicated, striated, rather solid. Sculpt n ri : 

 Protoconch with extremely fine and dense microscopic spiral striae ; 

 the following whorls strongly but irregularly radially striated, the 

 striae oblique, flexuous, retractive ; interstices with a few fine growth- 

 striae and microscopic fine dense spiral lines. Colour white, blotched 

 and marbled with reddish-brown on the spire-whorls, irregularly 

 radially banded with lighter brown on the last whorl. Epidermis thin, 

 membranous, slightly shining. Spire conoidal, obtuse, outlines nearly 

 straight, its height not quite two-thirds that of the aperture. Proto- 

 conch of lj whorls, convex. Whorls 5 to 5-|-, slowly increasing, lightly 

 convex, the last relatively high, more' or less distinctly angled at the 

 periphery ; base convex. Suture impressed. Aperture rather oblique, 

 rotundly lunate. Peristome thin, simple, regularly arched. Colu- 

 mella vertical, almost straight. Inner lip very little callous, reflexed 

 above, and sometimes partly hiding the narrow deep umbilicus, which 

 is about one-eighth of the minor diameter of the shell with 5 whorls. 



Diameter Maj., 10-25 mm. ; min., 9 mm. : height, 7-8 mm. 



Animal elongated, the foot long and narrow, reaching beyond the 

 shell, rounded behind, slightly truncated, and with a mucous gland 

 situated under a caudal papilla. Mantle subcentral, included ; body 

 roughish ; peduncles long, cylindrical, approximated at their bases ; 

 tentacles moderate. Top of the head yellowish-white; peduncles, 

 tentacles, and a line down each side of the head dark grey ; a broad 

 longitudinal band of white, with a dark -grey line in the centre, runs 

 along each side, and below this band the foot is edged with alternate 

 broad grey and narrow white bands. (Button.) 



Jnic arcuate, with flattened plaits, which indent the concave 

 margin. 



Rad'ula (Plate 1, fig. 14) with the formula 26 to 28 + 1 + 28 to 26 ; 

 laterals about 16. Central tooth rectangular, longer than broad ; the 

 reflexed portion short, sharply constricted near the base, and with ;i 

 small cutting-point. Laterals with the base oblique, the reflexed portion 



