![Thumbnail: [Volume 37, 1904 page 260]](/journals/rsnz/images/rsnz_37/thumbnails/rsnz_37_00_0286_0260_ac_02.gif)
Potamopyrgus corolla, Gould, sp.
Melania corolla, Gould, Proc. Bost. Soc. Nat. Hist., vol. ii. (1847), p. 223. Melania corolla, Reeve, Conch. Sc. (Melania), fig. 366. Amnicola corolla, Gould, U.S. Expl. Exp., vol. xii. (1852), p. 129, pl. ix., figs. 149 a-c. Paludestrina cumingiana, P. Fischer, Journ. de Conch., vol. viii. (1860), p. 208, pl. iv., fig. 7. Potamopyrgus corolla, Stimpson, Smithon. Miscell. Coll. No. 201 (1865), pp. 49, 50. Hydrobia crossei, Frauenfeld, Verh. Zool. Bot. Gesell. Wien, vol. xiv. (1865), p. 595. (?) Hydrobia ciliata, Frauenfeld, l.c., p. 1025. Bythinella corolla, Tenison-Woods, P.L.S. N.S.W., vol. iii. (1879), p. 135, pl. xiii., figs. 2, 3, 5. Hydrobia corolla, v. Martens, Crit. List N.Z. Moll. (1873), p. 14. Hydrobia corolla, Hutton, Manual N.Z. Moll. (1880), p. 83. Potamopyrgus cumingiana, Hutton, Trans. N.Z. Inst., vol. xiv. (1882), p. 144, pl. i., figs. A, F. Potamopyrgus cumingiana, Hedley and Suter, P.L.S. N.S.W. (2), vol. vii. (1893), p. 619. Potamopyrgus cumingiana, Suter, Journ. de Conch., vol. xli. (1893), p. 222.
Dr. Sturany, of Vienna, kindly informed me (in lit.) that Frauenfeld proposed the specific name crossei solely in case the name of Fischer, Paludestrina cumingiana, should be accepted, as there exists a Paludestrina cumingi, d'Orb., of earlier date.
Regarding the species Hydrobia ciliata, Gould, I am indebted to Dr. W. H. Dall, of Washington, for the following (in lit.): “Described as from Liberia with other shells from the missionary Dr. Perkins, but appears very similar to Hutton's figure in Trans. N.Z. Inst., vol. xiv., pl. i., fig. B 1. It seems as if some mistake had occurred, and this shell should really have come from New Zealand, but it is difficult to see how, as Gould was a very careful man.” Dr. P. Fischer no doubt admitted this species to be of African origin, for he says, “Nous connaissons deux autres espèces de la Nouvelle-Zélande, une des Antilles, une de l'Afrique; toutes sont caracterisée par la série d'épines qui ornent le dernier tour de spire.”† Pilsbry also, as already stated, gives West Africa as the habitat of Potamopyrgus, and is most likely alluding to the above species.
Dr. W. H. Dall (in lit. 20, xi., 97) also kindly sent me the following information respecting the type of the genus: “Melania
[Footnote] † Journ. de Conch., vol. viii. (1860), p. 209.
![Thumbnail: [Volume 37, 1904 page 261]](/journals/rsnz/images/rsnz_37/thumbnails/rsnz_37_00_0287_0261_ac_02.gif)
corolla, Gould (1847), is not corolla of Hutton, but the shell figured by Reeve as corolla. It is the largest, with spare long spines. The locality may have been erroneous. The whorls are rounded, cf. Hutton, Trans. N.Z. Inst., vol. xiv., pl. i., fig. A 1.” Considering this statement, we must conclude that the synonyms given by Hutton in his Manual, p. 83, are mostly correct, but that in his revision he took the wrong species for corolla—viz., Amnicola badia, Gould. He says (l.c., p. 143) that P. cumingiana, Fischer, which is held by v. Martens to be the same species as P. corolla, Gould, does not occur on Banks Peninsula, and that its dentition does not correspond with the description given by Dr. Stimpson. Now, Dr. Dall admits that the locality given by Gould may have been erroneous, and this appears now to be quite certain. I examined the dentition in typical specimens of P. corolla from the Ruamahanga River, Wairarapa, and I cannot say that it does not agree with Stimpson's description. The rhachidian and the lateral teeth correspond with his diagnosis, but the marginal teeth have a number of larger denticles, their number agreeing with Stimpson's statement, but there are a number of minute denticles besides which I am unable to count with a magnifying-power of 720. The number of denticles on the marginal teeth is variable, and can hardly be used for specific distinction.
The diagnosis of the species is as follows: Shell horn-colour, sometimes covered with a black coating, ventricose, thin, sub-pellucid; 6½ rounded whorls, the last three spinous, the others smooth and sometimes of a darker colour, the last swollen, subcarinated at the encircling series of spines. Spines long, rather distant, curved, directed upwards. Aperture ovate, peristome continous, thickened. There may be only rudimentary spines, or they may be absent altogether, leaving only a carina, or, finally, all the whorls may be smooth and convex, without a trace of a carina or spines. Length, 6.5 mm.; breadth, 4.5 mm. Ratio of B: L = 1: 1.44.
This species is distinguished by its globosely ventricose form, the absence of spines on the first 3½ whorls, the great number of spines on the last whorl (17 to 20), their length, curvature, and direction towards the apex.
My collection contains specimens from fourteen localities:—
(1.) Typical form with long spines is represented from Lakes Takapuna and Kanieri. Those from the latter locality have shorter spines. Most of the specimens are of horn-colour, sometimes with the first few whorls darker, and a few have a dark-brown coating.
(2.) Specimens with rudimentary spines occur in the creeks at Henderson and Swanson; in the creek at Hastwell's and
![Thumbnail: [Volume 37, 1904 page 262]](/journals/rsnz/images/rsnz_37/thumbnails/rsnz_37_00_0288_0262_ac_02.gif)
Ruamahanga River in the Forty-mile Bush; at Petone, near Wellington; Parua Bay, near Whangarei; and on the Chatham Islands. The majority of these specimens have a thick, black coating, and the continuous peristome much thickened.
(3.) With only a thread-like carina on the whorls there are specimens from Hastwell's and the Chatham Islands.
(4.) Shells with the whorls smooth, rounded, mostly coated with black and callous peristome, were found in creeks at North-cote, Hastwell's, Parua Bay, Kawau Island, the Waikato, and Chatham Islands.
(5.) Dwarf forms with spines, horn-colour, and six whorls, were collected in Lake Takapuna (3½ × 4½ mm.), and near Greymouth (4 × 6 mm.).
Type in the U.S. Nat. Mus., Washington.
Potamopyrgus corolla, Gould, subsp. salleana, P. Fischer, subsp.
Paludestrina salleana, P. Fischer, Journ. de Conch, vol. viii. (1860), pp. 208, 209, pl. iv., fig. 6.
Shell horn-colour, conical, thin; whorls 7 to 7½, flatly convex, the last four spinous, the others smooth, the last whorl with a chordate carina below the row of spines. The setæ are short, black, directed upwards. Aperture ovate, margins continuous, but little callous. Length, 6 mm.; breadth, 3½ mm. Ratio of B: L = 1: 1.7.
This subspecies differs from corolla in being more slender, less ventricose, in having spines on the last four whorls and a chordate carina below the row of spines; the last whorl is also less voluminous in proportion.
Although I have examined many hundreds of specimens I have not yet seen one with a chordate carina below the row of setæ, but some specimens from the Great Barrier Island and from Nelson are distinctly angled below the periphery, and I take this quite peculiar character mentioned by Fischer as of quite exceptional occurrence.
The distribution of this subspecies extends over a large area. In my collection there are specimens from Lake Takapuna, Western Springs (Auckland), Lake St. John, Onehunga Springs, Great Barrier Island, Maketu (Hunua Range), Waipoua River (near Masterton), Petone (near Wellington), Pelorus River, Nelson, and Collingwood.
All specimens are yellowish-brown, thinner than corolla, mostly without spines, and some are larger than the type. Length, 8 mm.; breadth, 4½ mm. The Nelson specimens are from brackish water.
Type in the collection of the Journal de Conchyliologie, Paris.