Potamopyrgus badia, Gould, sp.

Amnicola badia, Gould, Proc. Bost. Soc. Nat. Hist., vol. iii. (1848), p. 75; U.S. Expl. Exp., vol. xii. (1852), p. 126, fig. 150. Hydrobia fischeri, Dunker, Mal. Blätter, vol. viii. (1862), p. 152. Hydrobia reevei, Frauenfeld, Verh. Zool. Bot. Gesell. Wien, vol. xiii., p. 1024. Hydrobia fischeri, badia, reevei, v. Martens, Crit. List. N.Z. Moll., pp. 14, 15. Bythinella fischeri, badia, reevei, Hutton, Manual N.Z. Moll. (1880), p. 82. Potamopyrgus corolla, Hutton, Trans. N.Z. Inst., vol. xiv. (1882), p. 145, pl. i., figs. B, F (not of Gould). Potamopyrgus corolla, Hedley and Suter, P.L.S. N.S.W. (2), vol. viii. (1893), p. 619 (not of Gould). Potamopyrgus corolla, Suter, Journ de Conch., vol. xli. (1893), p. 619 (not of Gould).

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The type of this species is not spiny, the whorls moderately convex, shouldered above, and the dimensions given are: Length, ⅕ in. = 5 mm.; breadth, 1/12 in. = 2 mm.; ratio of B: L = 1:2.5.

This is the species that. since 1882 was erroneously called corolla by New Zealand conchologists. I have specimens from the River Avon which perfectly agree with the description and measurement given by Gould. Some are spinous, some shouldered and without spines, and others have smooth, flatishly rounded whorls. These typical specimens are, according to my experience, very rare, and it is curious that this form, instead of the very common one, should have been collected. The common form has the following dimensions—length, 5 mm.; breadth, 2½–3 mm.—having thus a somewhat greater angle of the spine. Both forms were found living together in the River Avon.

I know this species from the South Island only, and the finest specimens I found in the Rivers Avon and Heathcote, near Christchurch. Specimens from Akaroa have smooth, rounded whorls; a globose form, also smooth, and measuring 4 ½ × 3 mm., comes from Kowai Bush. Similar smooth forms are in my collection from Mount Somers, Bealey, Birch Hill (Tasman Valley), and Opawa, near Albury, the latter agreeing with H. fischeri. From the Leith, Dunedin, smooth and spinous forms are mixed, but the former are more abundant. I mentioned the occurrence of a large form of P. cumingiana from Lake Te Anau in these Transactions (vol. xxvi., p. 121), measuring 8 × 4 mm. Careful