ant that we should get acquainted with its dentition, and I therefore give here the figures of the jaw and part of radula.

The jaw is composed of twenty-five separate strongly papillate plaits. The radula has the formula 25—1—25; the central tooth is minute, unicuspid, the laterals and marginals bicuspid. For details in the dentition of this and the following three species of Phrixgnathus I refer to former publications by Professor Hutton and myself.

16. Phrixgnathus pumilus, Hutton, sp. 1883. Plate XVII., figs. 20, 21.

The jaw of this species was not seen by Professor Hutton when he examined the dentition. It is distinctly papillate, the plaits are narrow towards the ends, very broad in the middle; but this may differ with the individual.

The central and lateral teeth are just as figured by Professor Hutton (Trans. N.Z. Inst., xvi., pl. ix., fig. Q). The marginals, which are figured here, are similar to the laterals, bicuspid, but shorter, quadrate.

17. Phrixgnathus microreticulatus, Suter, sp. 1890. Plate XVII., figs. 22, 23.

This species was described by the writer as Hyalina microret., but on examining the jaw and radula I saw that it belongs to Hutton's Phrixgnathus.

The jaw is formed of about eighteen separate slightlypapillate plaits; the radula has the formula 27—1—27, the rachidian tooth unicuspid, the laterals and marginals bicuspid, the last exceptionally tricuspid.

18. Phrixgnathus allochroidus, var. lateumbilicatus, Suter, sp. 1890. Plate XVIII., figs. 24, 25.

This is another of my supposed Hyalinæ, which on examining the dentition turned out to be a Phrixgnathus; jaw with about twenty-one separate papillate plaits; formula of radula 14—1—14; central tooth tricuspid, with a median cutting-point, laterals and marginals bicuspid.

19. Ariophanta^* novaræ, Pfeiffer, sp. 1862. Plate XVIII., figs. 26, 27.

As mentioned in my list of the introduced land and freshwater mollusca of New Zealand (Trans. N.Z. Inst., vol. xxiv., p. 280), I suspected Mr. Musson's Zonitoides nitida, Müller, from Lake St. John, Auckland, to be not this species, but Pfeiffer's Hyalina novaræ. At my request Mr. Musson kindly sent me a number of shells and animals. I at once saw that

it could not be Z. nitida, but the specimens correspond with Pfeiffer's diagnosis of H. novaræ, with the only difference that some of Musson's specimens have ½—1 volutions more, and are therefore larger than the examples collected by Hochstetter. On examining the animal and dentition I saw that it is not a Flammulina, as first supposed, but an Ariophanta, the only species of this genus known to me to occur in New Zealand. It may therefore be of interest to have the dentition described and figured.

Jaw (fig. 26) membranaceous, smooth, upper margin arched, lower margin almost straight, with an indistinct median projection, ends tapering, faintly longitudinally and vertically striated.

Radula (fig. 27) tongue-shaped, formula 42—1—42, of which 10 to 12 are laterals; transverse rows of teeth straight. Central tooth long and narrow, with one long reflection, and a short, stout cutting-point, extending a little over the next row of teeth. Laterals broader, unicuspid, with a broad, blunt cutting-point of the same length as the central. A large number of intermediate teeth follow; they are oblique, with a bicuspid reflection, and one stout, oval cutting-point. Marginals sinuate, bicuspid.

20. Otoconcha dimidiata, Pfeiffer, sp. 1854. Plate XVIII., fig. 28, and Plate XIX., fig. 29.

Some time ago I found a single specimen of this curious mollusc at Port Hills, Lyttelton, the radula of which differs slightly from that described and figured by Professor Hutton (Trans. N.Z. Inst., vol. xvi., pl. ix., fig. Y). The specimen was rather a young one.

Jaw (fig. 28). It has hitherto been said that the jaw of Otoconcha is ribbed, and at first sight it would seem to be so. I have, however, quite a different opinion. The outlines of the jaw figured are decidedly those of an oxygnath jaw, which supposition is supported by the distinct longitudinal striation, which is very often seen in the jaw of the Limacidæ. The most irregular denticulation of the cutting-margin points to the fact that this jaw cannot be considered as ribbed, but as channelled by the action of the exceedingly strong cuttingpoints of the radula.

I therefore describe the jaw of Otoconcha as oxygnath, smooth, longitudinally striated, with a strong median projection inferiorly, irregularly channelled, the channels increasing in depth towards the cutting-margin, which is deeply and irregularly denticulated. Ends blunt.

The jaws of old animals represent only a narrow ledge with blunt denticulations on the inferior edge; perfectly worn out by the action of the teeth.