Potamopyrgus.} GASTROPODA. 231 



1. Potamopyrgus antipodum, Gray, 1843. Plate 14, fig. 2. 



Amnicola antipodanum, Gray, Dieff. N.Z., 241. Hydrobia antipodum. Gray, 

 Ereb. & Ter., 3, pi. 1, f. 19. above. Bythinella antipoda. Gray : Hutton, 

 M.N.Z.M., 81. Potamopyrgus antipodum, Gray: Hutton, T. N.Z.I., xiv, 

 145, pi. 1, f. C, except upper right figure; Suter, T.N.Z.I., xxxvii, 263. 



Shell small, ovate, acute, sometimes rimate, generally covered 

 with a brown earthy coat, smooth. Colour dark brown. Spire ele- 

 vated conic, higher than the aperture, outlines straight. Protoconch 

 small, acute, very often eroded. Whorls 7, regularly increasing, flatly 

 convex ; base convex. Suture not much impressed. Aperture ovate, 

 angled above. Peristome continuous, black, with a white inner callus, 

 Columella arcuate, very little reflexed. Operculum brown, horny, 

 paucispiral ; nucleus subcentral. 



Diameter, 3-2 mm. ; height, 6-1 nim. 



Dentition. Hutton, T.N.Z.I., xiv, 145, pi. 1, f. G. 



Type in the British Museum. 



Hob. Throughout New Zealand, very often in brackish water. 



Remark. The statement made by Von Martens that " some 

 specimens are bristly " is not correct. This species has never been 

 found with spines or a carina. 



Subsp. zelandiae, Gray, 1843. Plate 14, fig. 3. 



Amnicola (?) zelandice, Gray, Dieff. N.Z., 241. Hydrobia zdandice, Gray, 

 Ereb. & Ter., 3, pi. 1, f. 19, below. Bythinella zelandiae, Gray : Hutton, 

 M.N.Z.M., 81. Potamopyrgus antipodum, subsp. zelandice, Gray: Suter, 

 T.N.Z.I.. xxxvii, 263. 



This subspecies is distinguished from the species by its somewhat 

 smaller size, more tapering form, the generally more convex whorls, 

 and slightly deeper suture. 



Diameter, 2-5 mm. ; length, 5 mm. (type). 



Type in the British Museum. 



Hob. Nelson ; Wellington ; Wanganui ; Forty-mile Bush ; River- 

 head, Waitemata Harbour. 



Remark. It is much rarer than antipodum, but shows also a good 

 amount of variation. 



2. Potamopyrgus Badia, Gould, 1848. Plate 13, fig. 23. 



Amnicola Badia, Gould, P. Bost. S.N.H., iii, 1848, 75; U.S. Expl. Ex., 

 xii. 126, f. 150. Hydrobia Fischeri, Bunker, Mai. Blatt., viii, 1862, 152. 

 H. Beevei, Frauenfeld, V.Z.B.G. Wien, xiii, 1024. Bythinella Fischer i, 

 Badia, Reevei, Hutton, M.N.Z.M.. 82. Potamopyrgus corolla, Gould: 

 Hutton, T.N.Z.I., xiv, 145, pi. 1, f. B, not of Gould. P. Badia, Gld. : 

 Suter, T.N.Z.I., xxxvii, 264, 249. 



Shell small, ovate - conical, acute, thin, very frequently with a 

 black coating, imperforate. Sculpture consisting typically of a carina 

 on the shoulder, but usually there is a row of short spines on the last 

 3 whorls ; clean specimens show fine oblique growth -striae. Spire 



