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Potamopyrgus corolla, Gould, subsp. salleana, Fischer (1860).
Paludestrina salleana, P. Fischer, Journ. de Conch., vol. viii., 1860, p. 208, pl. iv., fig. 6.
(1.) Lake Waikare (Stat. 14 and 14F—Among reeds).—From Stat. 14 are thirteen adult and a number of young shells; from Stat. 14F twelve specimens, exactly the same as the former. Most of them are of horn-colour, with a white calcareous coating; three only are coated with black. All, with the exception of one, are spinous, the spines being distant, rather short, bent upward. In some specimens a distinct angle below the periphery is present. All the adult shells are smaller than the type, with six whorls. The dimensions range from 4½ × 2½ mm. to 5¼ × 3¼ mm.
(2.) Lake Rotoiti (Stat. 18—Dredged with weeds in 6 ft.).—Seventeen specimens of rather uniform size and shape, covered with a greenish-black coating. There are five rounded smooth whorls; only one specimen shows traces of bristles on the upper whorls. The peritreme is sometimes, not always, black. A few specimens are approaching corolla, being more ventricose than the subspecies. The dimensions vary from 5 × 3 mm. to 6 × 4 mm.
(3.) Lake Rotoiti (Stat. 18F—Dredged with weeds in 6 ft.).—Sixteen specimens, all “dead shells.” Very much the same as the preceding. Dimensions range from 5 × 3 mm. to 5½ × 3¼ mm.
(4.) Lake Taupo (Stat. 6—Dredged in 25 ft. to 420 ft.).—Many specimens, all light-horn colour, about two-thirds with smooth rounded whorls, the others with a carina above the periphery on which very short spines are situated, having a broad base, from which two to three separate spines arise. This is a feature met with in specimens of P. corolla from Lake Kanieri, South Island. The variability of the arrangement of the spines is just as great as in P. badia. The pullus is mostly brown and shining. The first two and a half whorls are always convex, never shouldered. The peritreme is continuous and brown. Young specimens have sometimes the body-whorl angled below the periphery, but no chordate carina is present. The size is very variable, ranging from 5 × 3 mm. with six whorls to 8½ × 5 mm. with seven whorls.
(5.) Lake Taupo (Stat. 6F—Dredged in 25 ft. to 420 ft.).—About two dozen specimens, showing the same characters as those of Stat. 6. The dimensions vary from 5½ × 3 mm. to 8½ × 5 mm., with six and seven whorls respectively.
(6.) Lake Taupo (Stat. 16F—Dredged in 280 ft. and 320 ft.,
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muddy bottom).—All the seven specimens are “dead shells,” therefore very fragile. They are shouldered, with traces of spines, covered with a dark-brown coating; no carina below the periphery. Dimensions range from 6½ × 4 mm. to 8½ × 5 mm.
(7.) Lake Taupo (Stat. 39—With weeds, from 20 ft. to 80 ft.).—There are seventeen specimens, of light-horn colour, and of an astonishing variability. Some call to mind the graceful, slender P. egenus, while others are more ventricose and short. Especially the elongated specimens show a very distinct angle on the body-whorl, arising from the junction of the outer lip with the whorl. Only a few are shouldered, but devoid of spines. The peritreme is dark-brown. The dimensions of four specimens are—4 × 2¾ mm.; 5½ × 2½ mm.; 6 × 3 mm.; 6 × 3½ mm. All adult specimens have six whorls.
(8.) Lake Taupo (Stat. 39F—With weeds, from 20 ft. to 80 ft.).—Four small specimens, covered with a grey coating, with six smooth convex whorls and a brown peritreme. They come very near P. antipodum, subsp. zelandiœ, but the whorls are more convex and the suture deeper. This is the most extreme form of salleana I have seen. The dimensions are—4 × 2¼ mm.; 4¼ × 2¼ mm.; 4½ × 2¼ mm.; 5 × 2½ mm.: the ratio of breadth to length varying from 1:1.6 to 1:2.
(9.) Lake Taupo (Stat. 40—With weeds, from 20 ft. to 80 ft.).—A large number of young specimens, most of which are distinctly angled below the periphery. Only two adult specimens, one smooth, one with spines. Colour, &c., the same as in examples from Stat. 39. The dimensions are 5 × 2½ mm. and 5 × 3 mm., with six whorls.
(10.) Lake Taupo (Stat. 40F—With weeds, from 20 ft. to 80 ft.).—Numerous young specimens, none adult, showing the same characters as those from Stat. 40, but they are covered by a green coating.
(11.) Lake Taupo (Stat. 47—Dredged in 400 ft.).—Four adult specimens, with a very thick black coating, very markedly shouldered, seven whorls, no spines, but there is an exceptionally strong carina; mouth snow-white. Dimensions, 7 × 4¼ mm.
(12.) Lake Waikaremoana (Stat. 3—Dredging in 50 ft. to 100 ft.).—Fifteen adult specimens, of a cinereous colour, with six whorls which are mostly shouldered and have rudimentary bristles; a few only have rounded smooth whorls. Peritreme light-brown. Dimensions range from 4½ × 2½ mm. to 6 × 3½ mm. These may be considered as typical forms.
(13.) Lake Waikaremoana (Stat. 17—Dredging in 800 ft.).—One specimen, a “dead shell,” with the last whorl broken off. It is thickly coated with calcareous substance, stained orange by oxide of iron. There are rudimentary spines visible on one
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whorl. Currents very likely brought this specimen to this considerable depth.
(14.) Lake Waikaremoana (Stat. 34—Dredging in 10 ft. to 20 ft.).—There are thirty-four adult shells, cinereous to black according to the amount of coating covering the shell. Most of them have six rounded smooth whorls, a few only are shouldered, none have spines. Peritreme brown. The dimensions vary from 5 × 2¾ mm. to 6½ × 3¾ mm. These also are typical examples.
(15.) Lake Manapouri (Stat. 15—From shallow water near the shore).—Two large adult specimens, both of which are of horn-colour, broadly shouldered, with distant brown spines on the carina, two or three arising from a common broad base. The larger example shows distinctly the slightly chordate carina below the row of spines on the last whorl, a character mentioned by P. Fischer. The other species, however, shows no trace of it; and it is, as I have pointed out elsewhere, not a constant but an extremely rare feature of salleana. The dimensions of the two shells are—8 × 5 mm. and 7 × 4 mm.
I have similar specimens from Lake Kanieri, kindly collected for me by Dr. Macandrew, of Hokitika, but they are more ventricose, and I assign them to P. corolla.