Fam. Limnæidæ.

Sub-fam. Ancylinæ.
Genus Gundlachia, Pfeiffer (1849).

Zeitschrift f. Malak., vol. vi., 1849, p. 98.

Gundlachia lucasi, n. sp. Figs. 10, 11.

Lake Waikare (Stat. 30 and 30F—Netting in weeds).—Three specimens; two of them were collected alive. Shell obliquely conical, thin, semitransparent, horn-colour, covered by a blackish coating; apex inclined to the right, situated at the posterior third of the length; convex anteriorly, slightly concave on the posterior slope; a few concentric lines of growth. Aperture oval; peritreme sharp, extremely fragile. No septum, the shells being in the Ancylus stage of development only. Dimensions of two specimens—Length, 3 mm.; breadth, 2 mm.; height, 1 mm.: length, 4 mm.; breadth, 2¾ mm.; height, 1½ mm. The dentition is very similar to that of the Gundlachia sp. from the River Avon,^* which, settles the generic position.

Fig. 10

Fig. 10a

This species stands nearest to G. tasmanica, T.-Woods. It is more rounded and elevated than the species from the River Avon. There is also one specimen of G. lucasi from Inglewood in my collection.

The occurrence of two species of Gundlachia in three different localities leaves no doubt that the genus is endemic, and accidental introduction out of the question.

Type in my collection.

I have great pleasure in uniting with the species the name of Mr. K. Lucas, who so ably and successfully collected the fauna of New Zealand lakes.

figured by Hutton. The number of laterals and marginals is very variable, and the figures sufficiently show the different arrangements of the cutting-points on the transitional teeth.

Sub-fam. Planorbinæ
Genus Planorbis (Guett.), Geoffroy (1767).
Planorbis (Gyraulus) corinna, Gray (1850).

P.Z.S., 1849, p. 167 (1850).

Lake Waikare (Stat. 33—Obtained by netting in weeds).—One specimen only was found, which has three whorls and a diameter of 2½ mm.

Genus Isidora, Ehrenberg (1831).

Isidora tabulata, Gould, subsp. moesta, H. Adams (1861). P.Z.S., 1861, p. 144.

(1.) Lake Waikare (Stat. 19—From reeds).—One specimen only was obtained. It is of light-horn colour, very thin, covered with a greenish coating; there are four whorls, the last two distinctly shouldered and keeled. Columella excavated in the middle, fold distinct, reflection of columellar lip small; outer lip sharp, regularly arched. It is a little more slender than the type. Shell: length, 7 mm.; breadth, 4 mm. Aperture: height, 5 mm.; breadth, 2½ mm. Ratios: i. = 1: 1.75; ii. = 1: 2; iii. = 1: 1.4. (The ratios are the same as in the revision of Isidora.)

(2.) Lake Waikare (Stat. 28—From weeds in water from 1½ ft. to 2 ft.).—Two specimens of dark-brown colour, solid and large, keeled, the keel becoming obsolete on approaching the aperture; columella twisted. They differ but little from the type. Shell: length, 17½ mm.; breadth, 11 mm. Aperture: height, 11 mm.; breadth, 6 mm. Shell: length, 14 mm.; breadth, 9½ mm. Aperture: height, 10 mm.; breadth, 5 mm. Ratios: i. = 1: 1.6; ii. = 1: 1.8; iii. = 1: 1.6. i. = 1: 1.5; ii. = 1: 2; iii. = 1: 1.4. The accompanying fig. 15 shows some teeth of the radula, which need no explanation. The dentition of our forms of Isidora is so variable that I doubt whether it can be used as a help to separate the species. However, a considerable number of animals of each species has to be examined before this point can be settled definitively.

Fig. 15

(3.) Lake Waikare (Stat. 28F—From weeds in water from 1½ ft. to 2 ft.).—Two “dead shells,” one young, the other nearly adult. They resemble those from the last station, but are a little more ventricose, and have the spire a little shorter. Shell:

length, 15 mm.; breadth, 10 mm. Aperture: height, 10 mm.; breadth, 5.5 mm. Shell: length, 9 mm.; breadth, 6½ mm. Aperture: height, 6 mm.; breadth, 3½ mm. Ratios: i. = 1: 1.5; ii. = 1: 1.8; iii. = 1: 1.5. i. = 1: 1.5; ii. = 1: 1.7; iii. = 1: 1.5.

Isidora lirata, Tenison-Woods (1879).

P.L.S. N.S.W., vol. iii., 1879, p. 138, pl. xiii., fig. 6.

(1.) Lake Rotoiti (Stat. 12—From weeds in 6 ft.).—Six specimens, one only adult. The colour is light-horny, some specimens having a dark coating; the whorls are rounded, but slightly flattened below the suture, the spiral striæ are present but not very distinct. Aperture produced at the base, columella twisted. They are slightly more ventricose than the type. Shell: length, 12 mm.; breadth, 7 mm. Aperture: height, 8½ mm.; breadth, 4 mm. Shell: length, 10 mm.; breadth, 6 mm. Aperture: height, 7 mm.; breadth, 3½ mm. Shell: length, 8½ mm.; breadth, 5½ mm. Aperture: height, 5 mm.; breadth, 3 mm. Ratios: i. = 1: 1.7; ii. = 1: 2.1; iii. = 1: 1.4. i. = 1: 1.7; ii. = 1: 2; iii. = 1: 1.4. i. = 1: 1.5; ii. = 1: 1.7; iii. = 1: 1.7.

(2.) Lake Taupo (Stat. 7—Dredged with weeds in 75 ft.).—One specimen of cream colour, fragile; four whorls, shouldered down to the middle of the last whorl, carina with short bristles; shell indistinctly spirally striated; columella twisted, aperture much produced anteriorly. More ventricose than the type. Shell: length, 8 mm.; breadth, 5 mm. Aperture: height, 6 mm.; breadth, 3 mm. Ratios: i. = 1: 1.6; ii. = 1: 2; iii. = 1: 1.3.

(3.) Lake Taupo (Stat. 38—With weeds, from 80 ft.).—Many, mostly young specimens. They are of a dirty-white colour with a thin whitish coating. Whorls 4, rounded, sometimes flattened below the suture, beautifully regularly spirally striate. Columella twisted, aperture produced anteriorly. These I consider to be typical forms. Shell: length, 9½ mm.; breadth, 6 mm. Aperture: height, 7 mm.; breadth, 3 mm. Shell: length, 8½ mm.; breadth, 4¾ mm. Aperture: height, 6 mm.; breadth, 3 mm. Shell: length, 7½ mm.; breadth, 4½ mm. Aperture: height, 5 mm.; breadth, 2½ mm. Ratios: i. = 1: 1.6; ii. = 1: 2.3; iii. = 1: 1.4. i. = 1: 1.8; ii. = 1: 2; iii. = 1: 1.4. i. = 1: 1.7; ii. = 1: 2; iii. = 1: 1.6. Fig. 16 shows some teeth of the radula. A remarkable feature are the additional denticles on the outer upper side of the marginal teeth.

(4.) Lake Taupo (Stat. 38F—With weeds, from 80 ft.).—Many, mostly young shells. Very much like the specimens from

Fig. 16