Isidora.] GASTROPODA. Gil 



B. Shell without spiral sculpture. 



a. Whorls convex, never distinctly shouldered. 



b. Height of spire about two-thirds that of the aperture. 

 c. Shell fusiform, impsrforate ; columella with a 



fold above . . . . . . . . antipodea. 



cc. Shell ovate, the last whorl ventricose, with an 



umbilical chink ; columella slightly twisted Hochstetteri. 

 bb. Height of spire eqxial to that of the aperture . . tabulate, 



aa. Whorls distinctly shouldered or convex. 



b. Height of spire a little less than that of the aperture ; 



columella with a prominent fold above . . novae -zelandicr. 



bb. Height of spire about two-thirds that of the aper- 

 ture ; columella somewhat twisted. Contour 

 resembling that of /. lirata . . . . . . moesta. 



1. Isidora antipodea, Sowerby, 1873. Plate 24, fig. 17. 



Physa antipodea. Sow., Conch. Icon., xix, f. 37 ; Button, M.N.Z.M., 30. 

 Aplexa antipoda, Sow : Hutton, P.L.S. N.S.W., vii, 67. Bulinus anti- 

 podeus, Sow. : Hutton, T.N.Z.I., xvii, 56 ; Hedley and Suter, P.L.S. 

 N.S.W. (2), vii, 627 ; Suter, J. de Conch., xli, 233. Isidora antipodea, 

 Sow. : Suter, T.N.Z.I., xxxvii, 273, f. o (reversed) ; xxxviii, pi. 19, f. 5. 



Shell fairly large, fusiform, thin and fragile. Sculpture formed by 

 fine slightly flexuous and close growth-lines, no spirals. Colour fer- 

 ruginous brown. Epidermis thin, opaque, not shining. Spire elevated, 

 conic, about two-thirds the height of the aperture ; outlines convex. 

 Protoconch small, rounded, mostly eroded. Whorls 4 to 4J. convex, 

 the last ovate, swelled in the middle. ; base flatly rounded. Suture 

 impressed. Aperture large, ovate, angled above. Peristome regularly 

 arched, thin and sharp ; base slightly effuse. Columella oblique, 

 with an oblique elevated fold above. I inter lip narrow, reflexed, and 

 perfectly covering the umbilicus, spreading as a thin layer over the 

 lightly convex parietal wall. 



Diameter, 12 mm. ; height, 22 mm. (from Sowerby's figure). Dia- 

 meter, llmm.; height, 18-5 mm. (aperture 6mm. by 12mm.). Pro- 

 portion of diameter to height. 1 : 1-7 to 1 : 1-8. Proportion of diameter 

 to height of aperture, 1 : 2. Proportion of height of aperture to height 

 of shell, 1 : 1-5 to 1 : 1-7. 



Animal unknown. 



Type in the British Museum. 



Hob. Lake Hayes, Otago ; Lake Wakatipu ; near Napier (fitle 

 F. Hutchinson, jun.). 



Remark. This seems, as far as our scanty knowledge goes, to be 

 the only one of our species that has constantly smooth whorls. 



2. Isidora Hochstetteri, Bunker, 1862. Plate 24, fig. 18. 



Physa Hochstetteri, Dkr., Malak. Blatter, ix, 1862, 150. P. guyonensis. 

 T. -Woods, P.L.S. N.S.W., iii, 1879, 138, pi. 13, f. 4 ; Hutton, M.N.Z.M., 

 30. P. guyonensis and Hochstetteri, Hutton, P.L.S. N.S.W., vii, 67. 

 Bulinus guyonensis and Hochstetteri, Hedley and Suter, P.L.S. N.S.W. (2), 

 vii, 627, 628. Bullinus guyonensis and Hochstetteri, Suter, J. de Conch., 

 xli, 232, 233. Isidora Hochstetteri, Dkr. : Suter, T.N.Z.I., xxxvii, 272, 

 f. 3 (reversed) ; xxxviii, pi. 19, f. 3. 

 20* 



